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NAGPUR INSTITUTE OF TECHNOLOGY Manufacturing process‐I

Question bank with solution

3rd

semeste

1

QUESTION BANK WITH

SOLUTIONManufacturing Process-I

B.E. III SemesterMechanical Engineering

By Prof. Naresh R. Tawale

H.O.D (Mechanical)

Nagpur Institute Of Technology, Nagpur





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STUDY OF SINGLE POINT CUTTING TOOL





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UNIT‐I

Q ‐1 Explain the tool geometry of single point cutting tool used on lathe with neat

sketches?

Classification of cutting tools: All the cutting tools used in metal cutting can be broadly

classified as:

Single point tools, i.e., those having only one cutting edge; such as lathe tools, shaper

tools, planer tools, boring tools, etc.

Multi‐point tool, i.e. those are having more than one cutting edge; such as milling

cutters, drills, broaches, grinding wheels etc. These tools may, for the sake of analysis,

be considered as consisting of a number of single point tools each forming a cutting edge. The cutting tools can also be classified according to the motion as:

a) Linear motion tools‐ lathe, boring, broaching, planning, shaping tools, etc.

b) Rotary machine tools‐ milling cutters, grinding wheels, etc.

c) Linear and Rotary tools‐ drills, boring tools, boring heads, etc.

Important terms: Before proceeding further, it would be advisable to be acquainted

with a few important terms related to the Geometry of single point tools. (See Fig)

Fig 1.1 different parts of single point cutting tool

1. Shank. It forms the body of a solid tool and it is this part of the tool which is gripped in the tool holder.





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2. Face. It is the top surface of tool between the shank and point of the tool. In the cutting action the chips flow along this surface only.

3. Point. It is the wedge shaped portion where the face and flank of the tool meet. It is cutting part of tool. It is also called nose, particularly in case of round nose tools.

4. Flank. Portion of tool which faces the work is term as flank. It is the surface

adjacent to and below the cutting edge when tool lies in a horizontal position.

5. Base. It is actually the bearing surface of the tool on which it is held in a tool holder or clamped directly in a tool post.

6. Heel. It is the curved portion at the bottom of tool where the base and flank of

the tool meet, as shown in Fig 1.

7. Nose radius. If the cutting tip (nose) of a single point tool carries a sharp cutting point the cutting tip is weak. It is, therefore, highly stressed during the operation

may fail or lose cutting ability soon and produces marks on the machined surface.

In order to prevent these harmful effects the nose is provided with a radius called

nose radius. It enables greater strength of the cutting tip, a prolong tool life and a

superior surface finish on the work piece. Also as the value of this radius

increases, a higher cutting speed can be used. But if it is too large it may lead to

chatter. So a balance has to be maintained. Its value normally raises from 0.4 mm

to 1.6 mm depending on several factors like depth of cut, amount of feed, type of

cutting, type of tool (solid or with insert), etc.

Principles angles of single point tools: The different angles provided on single point

tools play a significant role in successful and efficient machining of metals. The

thorough study of these tools angles is therefore must the main angles provided on

these tools are shown in Fig 5.4 and the average values of these cutting different

metals are given in chapter 6.





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Fig 1.2 Principles angles of single point of cutting tools

1. Rake angle. It is the angle form between the face of tool and plane parallel to its base. If this inclination is towards the inclination it is known as back rake or top

rake. When it is towards the side of tool it is called the side rake. These rake

angles guide the chips away from cutting edge thereby reducing the chip

pressure on face and increasing the keenness of the tool so that less power is

required for cutting. It is important to note that an increased rake angle will

reduced the strength of cutting edge. With the result, the tools used for cutting

hard metals are given smaller rake angles whereas those used for softer metals

contain larger rakes.

Negative rake. The rake angles described above are called positive rake angles.

When no rake is provided on the tool, it is said to have a zero rake. When the

face of tool is so ground that it slopes upward from the point it is said to contain

a negative rake. It obviously reduces the keenness of the tool and increases the

strength of the cutting edge. Such a rake is usually employed on carbide tipped

tools when they are used for machining extra‐ hard surfaces, hardened steel

parts and for taking intermittent cuts. A tool with negative rake will have a larger

lip angle, resulting in a stronger tool. Another advantage of negative rake,

particularly in case of tipped tools is that the tendency of the chip pressure is to press the tip against the body of the tool. This is obviously, a favorable factor for

tipped tools. The value of negative take o these tools normally vary from 5 to 10

degree.

2. Lip angle. The angle between the face and the flank of the tool is known as lip angle. It is also sometimes called the angle of keenness of the tool. Strength of

the cutting edge or point of the tool is directly affected by this angle. Larger the





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lip angle stronger will be the cutting edge and vice‐versa. It would be observed

that since the clearance angle remains practically constant in all the cases, this

angle varies inversely as the rake angle. It is only for this reason that when harder

metals are to be machined, i.e., a stronger tool is required, the rake angle is reduced and consequently the lip angle is increased. This simultaneously calls for

reduced cutting speeds, which is a disadvantage. The lip angle is, therefore, kept

as low as possible without making the cutting edge weak, that it becomes

unsuitable for cutting.

3. Clearance angle. It is the angle formed by the front or side surfaces of the tool which are adjacent and below the cutting edge when the tool is held in a

horizontal position. It is the angle between one of these surfaces and a plane

normal to the base of the tool. When the surface considered for this purpose is in

front of tool, i.e., just below the point, the angle formed is called front clearance

and when the surface below the side cutting edge is considered the angle formed

is known as side clearance angle. The purpose of providing front clearance is to

allow the tool to cut freely without rubbing against the surface of the job, and

that of the side clearance to direct the cutting thrust to the metal area adjacent

to the cutting edge.

4. Relief angle. It is the angle formed between the flank of the tool and a perpendicular line drawn from the cutting point to the base of the tool.

5. Cutting angle. The total cutting angle of the tool is the angle formed between the tool face and line through the point, which is a tangent to the machined surface

of the work at that point. Obviously, its correct value will depend upon the

position of the tool in which it is held in relation to the axis of iob.

Q ‐2 What are the various tool materials? Explain desirable properties of cutting tool

materials?

Various cutting tool materials have been used in industry for different applications. A

number of developments have occurred in the 20 th century thanks to aerospace and

nuclear programmer. A large variety of cutting tool materials has been developed to

cater to the variety of materials used in this programme. The important characteristics

of a cutting tool material are:





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i) Higher hardness than that of the work‐piece material being machined, so that it can be penetrating into the work material.

ii) Hot hardness, which is the ability of the material to retain its hardness at elevated temperatures in view of the high temperatures existing in the cutting zone. This requirement becomes more and more stringent with the increasing

emphasis on higher cutting speeds to bolster productivity.

iii) Wear resistance‐ The chip tool and chip work interfaces are exposed to such severe conditions, that adhesive and abrasion wear is very common. The cutting

tool material should, therefore, have high abrasion resistance to improve the

effective life of tool.

iv) Toughness—the tool, even though is hard, should have enough toughness to withstand the impact loads that come in the beginning of the cut or to force

fluctuations due to imperfections in the work material. This requirement is going

to be more useful for interrupted cutting, for example milling.

v) Low friction—the coefficient of friction between chip and tool should be low,

which would allow lower wear rates and better chip flow.

vi) Better thermal characteristics—Since a lot of heat is generated at the cutting zone, it is necessary that the tool material should have higher thermal

conductivity to dissipate this heat in the shortest time, otherwise the tool

temperature will become too high thus reducing its life. All these properties may

not be found in a single tool material. A comparison of the several of the cutting

tool materials is presented in Table 2.3. Improvements in tool materials have

been taking place over the past century to give us better cutting performance.

Q ‐3 Explain the necessity of a coolant in machining and its properties?

Cutting fluids sometimes referred to as lubricants or coolants are liquid and gases

applied to the tool and work‐piece to assist in the cutting operations.

Purpose of Cutting Fluids: Cutting fluids are used for the following purposes:

1. To cool the tool. Cooling the tool is necessary to prevent metallurgical damage and to assist in decreasing friction at the tool‐chip interface and at the tool‐work‐

piece interface. Decreasing friction means less power required to machine and

more important increased tool life and good surface finish. The cooling action of





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the fluids is by direct carrying away of the heat developed by plastic deformation

of shear plane and that due to friction. Hence, a high film‐coefficient for heat

transfer is necessary for a good coolant. For cooling ability, water is very

effective, but is objectionable for corrosiveness and lack of friction reducing wear.

2. To cool the work‐piece. The role of cutting fluid in cooling the work‐piece is to prevent its excessive thermal distortion.

3. To lubricate and reduce friction. (a) The energy or power consumption in removing metal is reduced: (b) abrasion or wear on the cutting tool is reduced

thereby increasing the life of the tool; (c) by virtue of lubrication, less heat is

generated and the tool, therefore, operates at lower temperatures with the

tendency to extend tool life; and (d) chips are helped out of the flutes of drills,

tapes, dies, saws, broaches, etc. An incidental improvement in the cutting

operation is that built‐up edge will be reduced which, in turn, will decrease

friction at the tool‐work‐piece area and contribute toward a cooler tool. It is

important to give the optimum cooling effect and lubrication condition in metal

cutting.

4. To improve surface finish. 5. To protect the finished surface from corrosion. To protect the finished surface

from corrosion, especially in cutting fluids made up of a high percentage of

water, corrosion inhibitors are effective in the form of sodium nitrate or

triethanolamine.

6. To cause chips break up into small parts rather than remain as long ribbons which are hot and sharp and difficult to remove from work‐piece.

7. To wash the chips away from the tool. This is particularly desirable to prevent

fouling of the cutting tool with the work‐piece.

Properties of Cutting Fluids: A cutting fluids should have the following properties:

1. High heat absorption for readily absorbing heat developed. 2. Good lubricating qualities to produce low‐coefficient of friction.

3. High flash point so as to eliminate the hazard of fire. 4. Stability so as not to oxide in the air. 5. Neutral so as not to react chemically. 6. Odorless so as not to produce any bad smell even when heated. 7. Harmless to the skin of the operators.





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8. Non‐corrosive to the work on the machine. 9. Transparency so that the cutting action of tool may be observed. 10. Low viscosity to permit free flow of liquid.

11. Low priced to minimize production cost.

Choice of cutting fluids: The choice of cutting fluid depends upon the following factors.

1. Type of operation 2. The rate of metal removal 3. Material of the work‐piece 4. Material of the tool 5. Surface finish requirement 6.

Cost of cutting fluids

Q ‐4 What is machinability of metal? What factors affect the machinability?

Machinability: Machinability of a material gives the idea of the case with which it can be

machined. The parameters generally influencing the machinability of a material:

1. Physical properties of the material. 2. Mechanical properties of the material. 3. Chemical composition of the material. 4. Micro‐structure of the material. 5. Cutting conditions. Since this property (machinability) of the material depends on various variable

factors, it is not possible to evaluate the same in terms of precise numerical values,

but as a relative quantity. The criteria of determining the same may be as follows:

1. Tool life. The longer the tool life it enables at a given cutting speed the better is the machinability.

2. Surface finish. It is also directly proportional, i.e.., the better the surface finish the higher is the machinability.

3. Power consumption‐ Lower power consumption per unit of metal removed indicates better machinability.

4. Cutting forces—The lesser the amount of cutting force required for the removal of a certain volume of metal or the volume of metal removed under

standard cutting forces the higher will be the machinability.



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ductile materials when how cutting speeds are used and adequate lubrication is not

provided. This causes excessive friction between the chip and tool face, leading to

the fracture of the chip into small segments. This will also result in excessive wear on

the tool and a poor surface finish on the work‐piece. Other factors responsible for promoting the production of discontinuous chips are smaller rake angle on the tool

and too much depth of cut.

1) Continuous chip.

Fig 1.4 continuous chip

As is evident from the name, the presence of separated segmental elements is

totally eliminated in this case. This type of chip is produced while machining a

ductile material, like mild steel, under favorable cutting conditions, such as high

cutting speed and minimum friction between the chip and the tool face. If

otherwise, it will break and from the segment chip. The friction at the Chip‐tool

interface can be minimized by polishing the tool face and adequate use of

coolant. Also, with diamonds tools the friction is less. The basis of the production

of a continuous chip is the continuous plastic deformation of the metal ahead of

the tool, the chip moving smoothly up the tool face. Other factors responsible for

promoting its production are bigger rake angle, finer feed and keen cutting edge

of the tool.





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2) Continuous chip with built‐up edge:‐

Fig 1.5 Continuous chip with built‐up edge

Such a chip is usually formed while machining ductile material when high friction

exists at the chip tool interface. The upward flowing chip exerts pressure on the

tool face. The normal reaction NR of the chip on tool face is quite high, and is

maximum at the cutting edge or nose of the tool. This gives rise to an excessively

high temperature and the compressed metal adjacent to the tool nose gets

welded to it. The chip is also sufficiently hot and gets oxidized as it comes of the

tool and turns blue in color. The extra metal welded to the nose or point of the

tool is called built up edge. This metal is highly strain hardened and brittle. With

the result as the chip flows of the tool, the built of edge is broken and carried

away with chip while the rest of it adheres to the surface of the work piece, making it rough. Due to the built up edge the rack angle is also altered and so is

the cutting force. The common factors responsible for promoting the formation

of built of edge are low cutting speed excessive feed, small rake angle and lack of

lubricant.

Adverse effects of built up edge formation:‐

a) Rough surface finish on the work piece. b) Fluctuating cutting force, causing the vibration in cutting tool. c) Chances of carrying away some material from the tool by the built‐up surface,

producing crater on the tool face and causing tool wear.

For avoiding the formation of built up edge the following precaution are

required.





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i) The coefficient of friction at the chip tool interface should be minimized by means of polishing the tool face and adequate supply of coolant the

operation.

ii) The rake angle should be kept large. iii) High cutting speeds and low feeds should be employed because at high

speed the strain of the weld becomes low. Similarly at very high

temperature also the strain of the weld becomes low.

Q ‐6 writes short notes on‐

i) Effect of cutting speed, feed and depth of cut on tool life

Effect of cutting speed‐ Out of all the above factors the maximum effect on tool life is of

cutting speed. The tool life varies inversely as the cutting speed, i.e., higher the cutting

speed the smaller the tool life. Generally, the reduction in tool life corresponding to an

increase in cutting speed is parabolic, as shown in fig 3. Based on pioneer work of F.W.

Taylor, the relationship between cutting speed and tool life can be expressed as:

.

Fig 1.6 Curve showing parabolic reduction in tool life with the increase in cutting speed.

VTn = C

V = Cutting speed (m/min)

T = Tool life (minutes)





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different variable, cutting speed, tool life, feed rate and depth of cut are interrelated as

given in the following imperical formula:

257

V = ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐m/min

T 0.19 x f 0.36 x t 0.30

Where, V = Cutting speed in m/min

T = Tool life in minutes

f = Feed rat in mm/min

and, t = Depth of cut in mm

For a given tool life the relationship among the other variables is also given by the

following imperical formula:

C

V = ‐‐‐‐‐‐‐‐‐‐‐‐‐

Fa x tb

Where, V = Cutting speed in (m/min) for the given tool life

f = Feed rat in mm/min

t = Depth of cut in mm

C = A constant

The expression ‘a’ and ‘b’ of (f) and (t) will depend upon the mechanical properties

of the workpiece material. From the expression‐‐‐‐‐‐‐‐above it is quite clear that if the

tool life is considered as constant the cutting speed (V) will decrease if the feed rate (f)

and depth of cut (t) are increased.





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ii) Tool Signature (ASA system)

The term tool signature or tool designation is used to denote a standardized system of

specifying the principal tool angles of a single point cutting tool. Some common systems

used for tool designation or tool nomenclature are the following:

1. American (or ASA) System. It declines the principal angles like side rake, back rake; nose etc., without any reference to their locations with regard to the

cutting edge. As such, this system of nomenclature does not give any inclination

of the tool behavior with regard to flow of chip during the cutting operation. The

three reference planes adapted for designating different tool angles are similar to

those used in conventional machine drawing, i.e., X‐X, Y‐Y and Z‐Z, the last one

containing the base of tool and the two planes being normal to this plane, as well as mutually perpendicular. Thus, this system is a coordinate system of tool

nomenclature.

2. British system. This system, according to B‐S 1886‐ 1952, defines the maximum

rate. The various tool parameters in this system are indicated in the order of Back

rake, Side rake, End relief angle, Side relief angle, End cutting angle, Side cutting

edge angle, and Nose radius.

3. Continental systems. This category of tool nomenclature systems includes the German or DIN System (DIN‐6581), Russian System (OCT‐BKC 6897 and 6898) and

Czechoslovakian System (CSN‐1226). The various tool parameters in these

systems are specified with reference to the tool reference planes.

4. International systems. It is an internationally adopted system, developed recently. It incorporates the salient features of tool nomenclature of different

systems in it.

It is a method of identification of tool angles standardized by the American Standards

Association (ASA), according to which seven important elements compromise the

signature of the single point cutting tool and are stated in the following angle.

Back rake angle, Side rake angle, Side relief angle, End cutting angle,

Side cutting edge angle, and Nose radius. It is used to omit the symbol for degrees and

mm, simply starting the numerical value of each element. For example a tool having tool

signatures as 10. 10, 6, 6, 8, 8, 2 will have the following angles.

Back rake angle = 10

Side rake angle = 10



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4. By a clamp type breaker in which a thin‐carbide plate or clamp is brazed or screwed on the face of the tool.

Effective control of the chip, as it moves across the face of the tool, may also be

achieved by proper selection of tool angel, feed, depth of cut and cutting fluids used. A large positive front rake gives rise to a looser chip formation, which flows down

the face of tool, and away from the work‐piece, leaving the newly cut surface

unscratched. A small positive or negative side rake has the effect of decreasing the

radius at which the chip coils. Hence the tendency to produce short, easily managed

chip. Slightly increased feed gives a thicker chip which breaks more quickly. A small

depth of cut with a fine feed allows the chip to form into comparatively small pieces

or direct it into swarf tray. The use of a good stream of coolant that acts as a

quenching medium causes the hot chip to become harder and break into small

pieces.

iii) Machinabiity index:

As mentioned in the previous article, the machinabiity of a material is

relative quantity. The machinabilites of different materials are compared

to in terms of their machinabiity indexes. For this purposes machinabiity

indexes are compared. The machinabiity index of this steel is taken

asd100. For computing the machinabiity index of any other material the

following relationship is used:

Machinabiity index (%)

Cutting speed of metal for 20 min. tool life

= ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ x 100

Cutting speed of standard free‐cutting steel for 20 min. tool life

But, this is only one methods used for determining machinability ratings of different

materials. The selection of a suitable criterion or method for evaluating the

machinability will depend upon the type of cutting operation. For example, a

comparison between the cutting forces required for machining a particular material

and those required for a standard material may form the basis of evaluating relative



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Basically in Orthogonal cutting, the cutting edge of the tool remains at right angles to

the direction of cutting velocity [Fig. 1.9 (a) or work feed, Fig. 1.9 (b)]. This type of

cutting is also as known as two‐dimensional cutting. In oblique cutting, the cutting edge

of the tool is inclined at an acute angle with the direction of the tool feed or work feed,

the chip being disposed of at a certain angle. This type of cutting is also called three‐

dimensional cutting. The main features of the two types of cutting are summarized as

below:

Orthogonal cutting

1. The cutting edge of the tool remains normal to the direction of tool feed or work feed.

2. The direction of the chip flow velocity is normal to the cutting edge of the tool.

3. The angle of inclination‘t’ of the cutting edge of the tool with the normal to the velocity Vt is ‘zero’.

4. The chip flow angle ‘β’, i.e., the angle between the direction of chip flow and the

normal to the cutting edge of the tool, measured in the plane of the tool face is

‘zero’.

5. The cutting edge is longer than the width of the cut. The last condition may not be fulfilled in some cases. It is then called semi‐

orthogonal or restricted orthogonal cutting.

Oblique cutting

1. The cutting edge of the tool always remains inclined at an acute angle to the direction of too feed or work feed.

2. The direction of the chip flow velocity is at angle ‘β’ with the normal to the

cutting edge of the tool. The angle is known as chip flow angle.

3. The cutting edge of the tool is inclined at angle ‘t’ with the normal to the direction of tool feed or work feed. i.e., the velocity Vt.

4. Three mutually perpendicular components of cutting forces act at the cutting edge of the tool.

5. The cutting edge may or may not be longer than the width of the cut.





3rd

semeste

22

LATHE MACHINE AND IT’S OPERATIONS





3rd

semeste

23

UNIT II

Q ‐1 with block diagram explains the working of a lathe machine mentioning various

directions in which the cutting tool can move.

Q ‐2 Name the various methods available for taper turning on a lathe machine. Explain

Set over method with a neat sketch.

Q ‐3 Why feed mechanism is used in lathe? Describe the working of feed mechanism.

Q ‐4 Explain in brief the Apron mechanism with neat sketch?

Q ‐5 what is the use of back gear? Explain the use of back gear?

Q ‐6 Explain threads cutting operation on Lathe machine

Q ‐ 7 Writes short notes on:

I) Lathe operations.

II) Time estimation for turning operation.

III) Carriage

IV) Dial chasing indicator

V) Lathe size and its specification





3rd

semeste

26

face of the tool approach the material to be cut. Usually the primary motion consumes

most of the cutting power.

Fig 2.3 Generation of a cylindrical surface by single point cutting tool.

2) The secondary motion is the one which feeds the tool relatively past the work piece.

The combination of the primary and the secondary motion is responsible for the generation of the desired surface.

Plane surface generation in shaping:‐

Plane surfaces can be generated when the work piece or the tool reciprocates for the

primary motion without any rotation. With the multi point tool generally plane surfaces

are generated. In this situation a combination of forming and generating is used to get a

variety of complex surfaces which are otherwise impossible to get through single point

tool operation. Some typical examples are spur gear hobbing and spiral milling of

formed cavities.





3rd

semeste

27

fig. no. 2.8 Generating a flat surface with a linear motion of a single point cutting tool

Q ‐2 Name

the

various

methods

available

for

taper

turning

on

a lathe

machine.

Explain

Set over method with a neat sketch.

Various methods are used for tapper turning on a job. The most common on these are

the following:‐

1. Tail stock Set Over method 2. By swiveling the compound rest



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8

3. 4. 5. B

1. TWhe

but t

angl

be t

1) The j

and twangle to

2) An al

the origi

Out of t

clampin

both th

position

part is

operato

be shift

stock, f

graduati

The req

On refe

x =

INSTITUTE

sing the ta

sing a for

y combing

AIL STOCK

n tapper t

he tip of t

of inclina

o method

ob revolve

centers, the cente

ternative

nal positio

he two the

bolt of th

front and

by a pre

o be obta

r and if th

ed toward

cing the h

ons a steel

ired amou

ring to fig

sin

OF TECHNO

pper turni

or broad

a longitudi

SET OVER

rning is p

e tool sho

ion should

s for acco

Fig.2.9 Tap

s in a posi

hile the t line of the

ethod ca

n and mov

tail stock

e tail stock

rear end o

etermined

ined on t

same is t

the oper

ead stock

rule can b

nt of tail st

.9 it will b

OGY

Question

g attachm

ose tool

nal and cro

ETHOD

rformed a

ld move a

be equal t

plishing th

er turning

ion, i.e. in

ool moves job.

be to shif

the tool p

ethod uti

is loosene

f the tail st

amount o

e tail sto

be obtai

tor. Grad

elp in adj

used for

ock set ov

seen that

ank with s

nt

ss feed in

t that tim

an inclina

o i.e. hal

ese relativ

y tail stoc

perfect ali

along the

the cente

arallel to t

lizes the s

d. Then, by

ock, the d

set over.

k side the

ed on the

ations pro

sting the

his purpos

r can be c

olution

special lat

the work

tion to the

f of the to

moveme

set over

gnment w

straight li

r line of th

e axis of t

cond met

means of

ad center

If the larg

center wi

head stoc

vided on

equired se

e.

lculated a

Manufacturi

he.

rotates an

center axis

al tapper a

ts.

ith the hea

e which i

work at a

e spindle.

od. For thi

the set scr

is shifted f

r diamete

ll be shift

side the

he flat sur

t over. In

follows:‐

g process‐I

d the tool

of the job.

ngle. Ther

d stock sp

inclined

n angle

s the nut o

w, provid

om the ori

of the tap

d toward

ead cente

face of th

bsence of

3rd

semest

feed

This

can

indle

t an

from

f the

d on

ginal

ered

the

will

tail

such





3rd

semeste

29

For a very small angle it can be safely considered that:

sin tan

x= L tan

D ‐ d

But, tan can also be taken = ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (considering triangle EFG or KLM)

2 l

D – d total taper

Therefore, x = L ‐‐‐‐‐‐‐‐‐‐‐‐‐ = Total length x ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐

2 l 2 x Taper length

Where x = required set over in mm

D = larger dia. In mm d = small dia. in mm

L = Total length of work in mm

L = length of tapered portion in mm

In case the job is to be tapered over its full length, l will be equal to = L. Therefore, the

set over will be given by:

D ‐ d Total Taper

x = ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ = ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐

2 2

2. BY SWIVELLING THE COMPOUND REST:‐

Steep and short external taper can easily be turned in lathe by swiveling the compound

rest on the carriage through an angle which is equal to half the total included angle of

the taper. The compound rest carries swivel plate under it. It is screwed to the cross

slide by means of a bolt and nut. The graduations on its periphery are in degrees. For

swiveling the compound rest the swivel plates is unscrewed and then rotated, along

with the compound rest, through the required angle. The graduations on the swivel

plates help in setting the compound rest at the desired inclination. Tool is then feed by

hand by rotating the compo und rest hand screw. The required inclination is calculated

by the formula:



NAGPUR

0

t

3. BY U

It is a v

As the

anywhe

with dif

I t is ca

maximu

mm.

INSTITUTE

Fig.2.

D

nα = −−−−

2L

ING THE

ry suitable

attachmen

re along th

erent man

able of tu

m, and the

OF TECHNO

0 turning t

d

−−−

APER – TU

method o

t travels

e length o

ufacturers

ning all cla

maximum

OGY

Question

aper swive

RNING AT

taper tur

long with

the job.

have a co

sses of tap

length of t

ank with s

ling the co

ACHMEN

ing which

the saddl

ll the tap

mon princ

ers of whi

he taper th

olution

pound re

:‐

provides a

e, it is p

r attachm

iple of wor

h the total

at can be t

Manufacturi

st

very wide

ssible to

nts thoug

king.

included

urned in o

g process‐I

ange of ta

urn the p

vary in d

ngle is 160

e setting i

3rd

semest

pers.

aper

sign

as a

235





3rd

semeste

32

After every cut, the feed to the tool is given by moving the compound restwhich is

poisoned parallel to the cross‐ slide, i.e. , at 900 to the axis of the job. The required

angle can easily be found out from the relation:

D – d

Tan = ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ all dimensions are in mm

2L

D ‐ d

= tan‐1 ‐‐‐‐‐‐‐‐‐‐‐‐ (degrees)

2L

Or

In some taper turning attachment it will be observed that the bracket instead of having

graduations in degrees carries divisions in mm. in such cases we have to find out no. of

mm divisions through which the guide plate should be swiveled instead of calculating

the angle . These divisions can be found out from the formula:

D ‐ d

M= ‐‐‐‐‐‐‐‐‐‐‐‐ x C

2L

Where, M = the required no. of mm divisions through which the guide plate is to be swiveled.

D = Larger dia. In mm

D = Smaller dia. In mm

L = Length of taper in mm

C = half of the total length of guide plate in mm.

ADVANTAGES OF USING A TAPER TURNING ATTACHMENT:‐

1. Its setting is very easy and can be done very quickly. 2. Its use does not call for too much of skill on the part of the operator. 3. Accurate can be readily be obtained in a single setting.



NAGPUR

3

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a

5. I6. I

b

4. USIN

Very sh

cutting

cause a

in cutti

maximu

Q ‐3 Wh

the wor

The gea

reversin

INSTITUTE

ormal set‐

uring the o

lignment o

is equally ts use ena

ecause lon

G A FORM

F

rt tapers

edge of th

lot of vibr

g. Theref

m 20 mm l

y feed me

king of fee

r mechanis

g mechan

OF TECHNO

up and al

peration, a

r the comp

suitable fole a bette

gitudinal p

OR BROA

ig. 2.12 Ta

can easily

e tool is g

tions and

re while u

ength. Use

chanism (t

d mechani

m operate

ism. This i

OGY

Question

ignment o

s in other

ound rest i

external ar surface fi

wer feeds

NOSE TO

er turning

e turned

ound to c

hatter bec

sing this

of heavy a

umbler re

m?

d by mean

s used fo

ank with s

the lathe

ethods ei

s to be swi

s well as innish and e

can easily

L:‐

by using b

with the f

ontain hal

ause the f

ethod for

d rigid typ

ersing me

of the fe

providin

olution

and its m

ther in two

eled.

ternal tapensure an i

be employ

oad nose

rm or bro

taper ang

ll cutting

turning v

e of lathe

chanism) i

d reverse

power f

Manufacturi

ain part is

centers ar

rs. crease rat

d

ool

ad nose to

le Use of

dge of the

ry short t

ill increas

used in l

lever is call

eds to th

g process‐I

not distrib

e thrown o

of produ

ol in whic

uch a too

tool is inv

per, say u

this limit.

athe? Des

ed the tu

carriage.

3rd

semest

uted

ut of

tion

the

l will

lved

p to

ribe

bler

The





3rd

semeste

34

motion from the spindle to the lead screw or to the feed rod is transmitted through this

mechanism.

Refer fig

Fig.2.13 Feed mechanism and change gears

Gear G1 is mounted on the rear end of the spindle S. the feed mechanism consist of the

gears G2, G3 and G4 and is operated by means of feed reverse lever F. When the lever

operated from the center position to either the top or the bottom position one of the

gear G2 or G3 will mesh with the gear G1 where as these two gears always mesh with

each other mutually. Thus, it will be seen that in top position of the lever F motion is

transmitted from gear G1 to G4through gear G3 and gear G2 plays no role with the

result the gear G4 will have the same direction of rotation as the spindle fig (a).

Against this, in lower position of the lever F, motion from G1 is transmitted to G4

through G2and G3 respectively as shown in fig (b). This will enable G4 to rotate in a

direction opposite to that of the spindle S. It will be evident that when the lever will be

in its central position neither of gears G2 and G3 will be meshing with G1 and thus the

feed mechanism will be disengaged. The above mechanism is usually enclosed in the

head stock except the lever F which is kept projecting outside.





3rd

semeste

35

On the same end, as the above mechanism, but outside the headstock, there is another

set of gears called Change gears. This consist of gears G5, G6, G7and G8. Etc. Gear G5 is

mounted on the same spindle as G4 and thus rotates at the same speed as the latter.

This transmits the motion to gear G8 through G6 and G7, which further transmit it to the lead screw or the feed rod. These four gears are known as change gears for the

reason that they can be removed and replace by the other gears having different no of

teeth. A desired speed of lead screw or feed rod can be obtained by selecting the

suitable change gears having proper no of teeth. Gears G6 and G7 are usually mounted

on the stud and are known as stud gears. A quadrant is provided and the stud can be

shifted along its straight slot to enable proper meshing of change gears. Also, this

quadrant can be swung vertically along the slot P to enable meshing of gear G5 and G6.

When proper meshing has been acquired the quadrant is locked in position. Gear G8 is

mounted directly on the lead screw on those lathes which do not have a feed gear box,

where it is mounted on the gear box driving shaft in those lathe which carry the gear

box.

Q ‐4 Explain in brief the Apron mechanism with neat sketch?

Apron:‐

It is the hanging part in front of the carriage. It serves as housing for no of gear trains

through which power feed can be given to the carriage and cross‐ slide. Also it carries the clutch mechanism and split half nut. Out of these two, the former (clutch

mechanism) is used to transmit motion from the feed rod, whereas the latter, in

conjunction with the lead screw, moves the whole carriage in thread cutting.

Apron Mechanism:‐

Through this mechanism power feeds can be given to the carriage and cross‐ slide.

Construction:‐

H is the hand wheel for providing the longitudinal hand feed to the carriage.H1 is the

hand wheel for providing hand feed to the cross slide. Lever L1 is for engaging or

disengaging the power feed to the carriage and cross slide. Star wheel S is operated

when power feed is to be engaged. Lever L2 operates the split half nut N to engage or

disengage the same from lead screw L. D is the chasing dial used in thread cutting.



NAGPUR

6

Inside t

rear en

Spindle

the rackby lever

gear G3

free an

the Gea

always i

Spindle

Gear G9

which c

when w

drawn i

the S5 d

disenga

of G9 an

INSTITUTE

e apron t

and han

S2 carries

provided L1. This le

with G4wh

is not me

r G2. Spindl

n mesh wit

S5 is just b

is not rigi

n be dra

e want to

. this ena

riven by t

e the sam

d the trans

Fig. 2.1

OF TECHNO

ere are 5

wheel at

nother ge

at the froner has thr

ich is mou

sh with an

e S4 in add

h gear G6

elow the s

ly secured

n in or pu

ransmit th

le tempor

e lead scr

e, the star

mission is

4 Apron m

OGY

Question

pindles S1,

the front.

r G7 at its

t of the late position

ted on sp

y other ge

ition to ge

hich is mo

pindle S3 a

to S5. Clu

hed out b

e motion f

rily rigid f

w throug

heel is ro

topped.

chanism u

ank with s

S2, S3, S4

G1 is in m

ear end, o

he. Spindls 1, 2 and

indle S4.In

r. In posit

r G4 carrie

unted on t

nd it carri

ch T is pro

rotating t

om the le

stening b

the wor

tated in th

se in lathe

olution

nd S5.Spin

esh with

utside the

S3 carries . In positi

position 2

ion 3 i.e. t

s another

he screwe

s gear G8

vided at t

he spindle

d screw to

tween S5 a

W and g

reverse d

Manufacturi

dle S1 carri

2 mounte

apron, whi

gear G3 wn 1 i.e. lo

i.e. the mi

p, the ge

ear G5 at i

spindle o

and G9 wit

e rear en

by means

the spindl

nd G9, wit

ear G9. W

irection to

g process‐I

s gear G1

on spindl

ch meshes

ich is opeest, it eng

dle; Gear

r G3 mesh

ts rear end

the cross

h the wor

of this sp

of star wh

e S5 the sp

the result

en we wa

push the cl

3rd

semest

t its

e S2.

with

ated ages

G3 is

with

. It is

lide.

W.

indle

el S.

indle

that

t to

utch





3rd

semeste

37

WORKING:‐

When hand feed is required to be given to the carriage or the cross slide, lever L1 is put

in position 2 so that the gear G3 neither engaged with G4 nor with G2. When power feed

is to be given to the carriage, lever L1 is put in position 3 so that G3 meshes with G8 and

G2 simultaneously. Star wheel is tightened to connect G9 with S5. Motion is transmitted

from the lead screw to the G9, through the worm and hence to S5 and G8. It is further

transmitted to G2 and hence G7, they being on the same spindle. G7 meshes with the

fixed rack and, therefore, the carriage is moved. To give power feed to the cross slide

lever L1 is put in position 1, so that the gear G3 meshes with the G4. Now the

transmission of the motion from the lead screw is to the worm then to G2 and G8 and

finally to G3 through G4 and G5.

This mechanism is not capable of providing power feed to both lead screw and cross

slide simultaneously.

Q ‐5 what is the use of back gear? Explain the use of back gear?

Back geared Headstock:‐

CONSTRUCTION:‐

The back geared head stock consist of a casing accommodating the main Spindle, the

three or four step cone pulley and the back gears. The internal mechanism of this type

of head stock is shown in fig. In this, a step cone pulley is mounted on the main spindle,

which carries a spur gear G1 at its one end and a pinion P1 at the other. Gear G1 is firmly

keyed to the spindle so that it can never revolve free. The spindle carries a sleeve over it

which is a loose fit. The cone pulley is firmly secured to this sleeve. Also, the pinion P1 is

firmly secured to this sleeve. This arrangement forces the pinion P1 to revolve with the

cone pulley under all conditions. A spring knob K engages the gear G1 with the cone

pulley. The cone pulley is driven by means of a belt, through a countershaft, by an

electric motor. This spindle enables four different speed of spindle.

Use of back gears (WORKING):‐

The back is used for effecting reduction in spindle speeds, there by facilating a wider

range of speeds. The back gears are mounted on an eccentric shaft which is operated by

means of hand lever known as back gear engaging lever (L). The back gears consist of

spur gear G2 (opposite pinionP1) and a pinion P2 (opposite gear G1). When speed





3rd

semeste

38

reduction is desired, the knob is pulled out to make the cone pulley free of gear G1 and

hence the spindle. The back gears are put into mesh with the spindle gears by pulling in

the eccentric shaft. Now the sequence of transmission of motion and power is such that

the cone pulley is driven by the motor through the belt. With the result the pinion P1

revolves. This being in mesh with gear G2, transfers the motion to latter which, in turn,

revolves the eccentric shaft and hence the pinion P2.This, further being in mesh with

gear G1, transmit the motion to the latter and hence to the Spindle.

Q ‐6 Explain threads cutting operation on Lathe machine

PRINCIPLE OF THRESD CUTTING:‐

Thread cutting is one of the important operations performed on lathe. The principle of

thread cutting is to produce a helical groove on a cylindrical or conical surface by

feeding the tool longitudinally when the job is revolved between centers or by a chuck.

The longitudinal feed should be equal to the pitch of the thread to be cut per revolution

of the work piece. The leadscrew of the lathe, through which the saddle receives its

traversing motion, has a definite pitch. A definite ratio between the longitudinal feed

and rotation of the headstock should therefore be found out so that the relative speed

of rotation of the work and the leadscrew will result in the cutting of a screw of a

desired pitch. This is affected by change gears arranged between the spindle and

theleadscrew or by change gear mechanism or feed box used in a modern lathe where it

provides a wider range of feed and the speed ratio can be easily and quickly changed.

THREAD CUTTING OPERATION:‐

In thread cutting operation the first step is to remove the excess material from the

work‐piece to make its diameter equal to the major diameter of the screw thread.

Change gears of correct size are then fitted to the end of the bed between the spindle

and the leadscrew. The shape or form of the threads depends on the shape of the

cutting tool to be used.

In a metric thread, the included angle of the cutting edge should be ground exactly 600.

The top of the tool nose should be set at the same height as the center of the

workpiece. A thread tool gauge is usually used against the turned surface to check the

cutting tool so that each face of the cutting tool may be equally inclined to the center





3rd

semeste

39

line of the workpiece. The speed of the spindle is reduced by one half to one fourth of

the speed required for turning according to the type of the material being machined,

and the half nut is then engaged. The depth of cut which usually varies from 0.05 to 0.2

mm is applied by advancing the tool perpendicular to the axis of the work or at an angle equal to one half of the angle of the thread, and 30

0 in the case of the metric thread, by

swiveling the compound rest. Except when taking very light finishing cuts, the latter

method is superior to the former as it

1. Permits the tool to have a top rake; 2. Permits cutting to take place on one edge of the tool only. 3. Allow the chips to slide easily across the face of the tool without crowding.

4. Reduces cutting strain that acts on the tool. 5. Reduces the tendency to cause the tool to “dig‐in”.

After the tool has produced a helical groove up to the end of the work this is quickly

withdrawn by the use of the cross‐slide, the half nut disengaged, and the tool is brought

back to the starting position to give a fresh cut. Before re‐engaging the half nut it is

necessary to ensure that the tool will follow the same path it has traversed in the

previous cut, otherwise the job will be spoiled. Several cuts are necessary before the full

depth of thread is reached. Arising from this comes the necessary to “pickup” the

thread.

Cutting right hand and left hand threads:

When cutting the right hand threads the carriage must move towards the head stock,

for a left hand thread the carriage must moves from the headstock and toward the

tailstock. The job moves as always, in the anticlockwise direction when viewed from the

tailstock end. As previously mentioned the direction at which the carriage moves in

relation to the lathe headstock is controlled by means of the tumbler gears or bevel gear

feed reversing mechanism.

Cutting multiple threads:

In a piece of the work it is possible to have several separate and independent threads

running along it. Accordingly, there may be single threaded screw and multiple or multi‐

start threaded screw. The independent threads are called starts. For one complete turn





3rd

semeste

40

round the screw when there is a movement of one threads the screw is called single

threaded screw but when there is a movement of more than one thread the screw is

called multi or multi‐ star threaded screw. In the case of, a three start thread, for one

complete turns the thread advance three times as far as if it was a single thread. The distance the multiple screw thread advances along its axis in one turn is called lead.

The calculation for the multi –start thread are identical with those required for a single

start thread. The ratio depends upon the relationship between the pitch of the lead

screw of the machine, and the lead, but not the pitch, of the thread to be cut.

This may be written as:

Driver Pitch Lead o f the screw to be cut

‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ = ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐Driven Pitch Pitch of the Lead screw

The cutting procedure of multi start thread is similar to that of single start threads. In

multi‐ start threads, circumference of the job should be divided equally in to as many

part as there are starts on the threads, and every parts or division of the circumference

of the job becomes the starting point for the new thread.

Cutting tapered thread:‐

The surface is first turn taper to the required angle by any one of the taper turning

methods described before. The thread cutting tool is then set perpendicular to the lathe

axis and not to the tapered surface. To produce an accurate thread a taper turning

attachment is used. This is swiveled to be the half taper angle. The thread is finished in

the usual manner.

Q ‐ 8 Writes short notes on:

I. Lathe operations:‐The various operations have been performed on the lathe machine to generate the

desired shape.

a) Turning:‐





3rd

semeste

41

Turning is by far the most commonly used operation in a lathe. In this, the work held in

the spindle is rotated while the tool is fed past the work piece in a direction parallel to

the axis of rotation. The surface thus generated is a cylindrical surface.( fig 4.1)

b) Facing :‐

Facing is an operation for generating flat surfaces in lathes. The feed, in this case, is

given in a direction perpendicular to the axis of revolution. The tool used should thus

have an approach angle suitable so that it would not interfere with the work piece

during the tool feeding.

Also, the radius of work piece at the contact point of tool varies continuously, as the

tool approaches the center. Thus, the resultant cutting speed continuously varies in

facing, starting at the highest value at the circumference, to almost zero near the

center. Since the cutting action and the surface finish generated depend on the actual

cutting speed of the work piece, due carte has to be taken of this fact.

c) Knurling:‐

Knurling is a metal working operation done in a lathe. In this, a knurling tool having the

requisite serrations is forced on to the work piece material, thus deforming the top

layer, as shown in fig. this forms a top surface, which is rough and provides a proper

gripping surface.

d) Parting :‐

Parting and grooving are similar operations. In this, a flat‐ nosed tool would plunger cut

the work piece with a feed in the direction perpendicular to the axis of revolution, as

shown in fig. This operation is generally carried out for cutting off the part from the

parent material. When the tool goes beyond the center, the part would be severed.

Otherwise, a rectangular groove would be obtained. It is also possible, in similar

operation, to use a special form of a tool to obtain the specific groove shape.

e) Drilling:‐

Drilling is the operation of making cylindrical holes into the solid material, as shown in

fig. A twist Drill is held in the quill of the tailstock, and is fed into the rotating work piece

by feeding the tailstock quill. Since the work piece is rotating, the axis of the hole is well‐

maintained, even when the drill enters at an angle initially. The same operation can also





3rd

semeste

42

be used for other hole making operations, such as center drilling, counter sinking, and

counter boring. This operation is limited to holes through the axis of rotation of the

ends.

f) Boring:‐

Boring is the operation of enlarging a hole already made by a single point boring tool

turned as boring bar, as shown in fig. The operation is somewhat similar to the external

turning operation. In view of the internal operation, it is more restricted. The cutting

forces experienced are somewhat more than the external operation. Also, the tool used

is less rigid compared to tuning tool, and as a result, it cannot withstand the large

cutting forces. Thus, the process parameters used are somewhat lower than those used

for turning. Boring is used for generating an accurate hole with good surface finish.

II. Time estimation for turning operation:‐

The total time in completing the job by machining will includes many factors such as

actual time taken in machining (cutting time), time required in setting of job, time

required in setting of tool or tools and handling time, etc. The method of computing the

actual machining or cutting time is given below:

Suppose the work is to be turned through the length of l mm

l1 = the distance required for feeding the tool crosswise, to increase the depth of cut in

mm.

l2 = over travel of the tool in mm at the end of the each cut.

t = Depth of cut in mm.

f 1= feed in mm per revolution.

N = speed in rpm of the work.

n = total no of cuts taken for obtaining the required diameter of the feed.

L1 = total distance, in mm that the tool travels in the direction of the feed.

Now, the distance travel by the tool in the direction of the feed in a single cut

= l + l1 +l2 = L (say)





3rd

semeste

43

Therefore, the total distances L1is given by:

L1 = L x n mm

Also the amount of feed (f) per minute is given by

f = f 1 x N mm

The Time T, in minutes, required for the tool to move through the complete length L1

mm will be computed by the formula:

L1

T = ‐‐‐‐‐‐‐‐‐‐‐minutes

f

L x n

= ‐‐‐‐‐‐‐‐‐‐‐‐minutes

f 1 x N

III. Carriage:‐

The lathe carriage serves the purpose of the supporting, guiding and feeding the tool against the job during the operation on the lathe. It consists of the following main

parts.

Fig. the carriage





3rd

semeste

45

engaged. If the dial turns, the graduations pass a fixed reference line. The half ‐ nut is

closed for all even threads when any line on the dial coincides with the reference

line. For all odd threads, the half nut is closed at any number line on the dial

determined from the charts. If the pitch of the thread to be cut is an exact multiple of the pitch of the lead screw, the thread is called even thread otherwise the thread

is called odd thread.

In case of dial the rule for determining the dial division is:

In the case of metric thread, the product of the pitch of the lead screw and the

number of the teeth on the worm wheel must be an exact multiple of the pitch of

the thread to be cut. In the case of the English threads, the product of the threads

per inch to be cut and the number of teeth on the worm wheel must be an exact multiple of the number of threads per inch of the lead screw. For example, if the

pitch of the lead screw is 6 mm and the worm wheel has 15 teeth, the product will

be 90, such as 1, 1.25, 1.5, 2, 2.25, 3, 3.75, 4.5, 6, 7.5, 9, 10, 15, 30, 45, 90, may be

pick up when any line of the dial coincide with the reference line. For picking up the

threads of different pitches, a set of worm wheel is used to give desired value.

V) Lathe size and its specification: In order to specify the lathe, the no. of parameters is used based on the specific

applications. The major elements used for specification should invariably be based

on the components that are manufactured in the lathe. The following are the basic

elements generally specified for the capability of the lathe machine. Fig

• Distance between centers:‐ specifies the maximum length of the job that can be

turned in the lathe. • Swing over the bed: ‐ specifies the maximum diameter of the job that can be

turned in the lathe machine, generally restricted to small length jobs.

• Swing over the cross slide:‐ specifies the maximum diameter of the job that can

be turned in the lathe machine with the job across the cross slide, which is

generally the case





3rd

semeste

46

Through the above gives the basic capacity of the machine as shown in fig. there are a

no. of other factors that should also be specified to fully describe the lathe machine.

They are:‐

• Horse power of the motor.

• Cutting speed range.

• Feed range.

• Screw cutting capacity

• Accuracy achievable

• Spindle nose diameter and hole size.





3rd

semeste

47

SHAPER MACHINES AND SLOTTING MACHINES





3rd

semeste

48

Unit III

Q ‐1 Explain with neat sketch crank and slotted lever mechanism used in shaper? Show how the Quick

return of tool is accomplished.

Q ‐2 what are the various shaper operations?

Q ‐3 Explain with neat sketch Whitworth quick return mechanism used in shaper?

Q ‐4 what are various parts and their functions of slotter machine?

Q ‐6 Explain in short with neat sketch the Hydraulic mechanism in shaper machine.

Q ‐7 Explain with neat sketches:‐

i) Table feed mechanism in shaper.

ii) Q ‐13 describes in brief the puncher slotter and tool room slotter.

Q ‐8 State the function of the following parts of shaper.

i) Cross rail

ii) Clapper box

iii) Tool head

Q ‐ 9 what are the various parts and their functions of shaper machine?



NAGPUR

9

Q ‐1 Exp

how th

Ans‐ cr

transmi

individu

bull gea

on the s

to the c

the cra

at a uni

within t

pivoted

the roc

rotates

will rota

in the s

Thus, thram.

INSTITUTE

lain with n

Quick ret

nk and sl

ted to the

al motor o

r may be c

tep cone p

ntre of th

k pin 11 is

form spee

he slotted

at 15 at it

er arm is

causing th

te on the

lotted link

e rotary m

OF TECHNO

eat sketch

rn of tool

otted link

bull gear

overhead

anged by

ulley. Bull

bull gear

fitted. Rot

. Sliding b

link 9. Th

bottom e

forked and

crank pin

rank pin ci

9 giving it

otion of th

OGY

Question

crank and

is accompl

mechanis

4 through

line shaft

ifferent c

ear 14 is

is radial sli

ation of th

lock 12 w

slotted li

d attache

connecte

to rotate t

rcle, and a

a rocking

e bull gear

ank with s

slotted li

ished.

is as sh

the pinion

hrough sp

mbination

large gea

e 16 whic

bull gear

ich is mou

k 9 whic

to the fr

to the ra

he sliding

the same

ovement

is convert

olution

k mechani

wn in fig.

1 which r

ed control

of gearing

mounted

carries a

will cause

nted upon

is also kn

me of the

m block 8

lock 12 fa

time will

which is c

d to recip

Manufacturi

sm used i

The moti

ceives its

mechanis

for simply

within the

sliding blo

the crank

the crank

own as th

column. T

by a pin.

tened to t

ove up an

ommunica

rocating m

g process‐I

shaper? S

n or pow

otion fro

. Speed o

hifting th

column. B

k 10 into

in 11to re

pin 11 is

rocker a

e upper e

s the bull

he crank pi

down th

ed to the

ovement o

3rd

semest

how

er is

an

f the

belt

lted

hich

olve

itted

m is

d of

gear

n 11

slot

ram.

f the





3rd

semeste

50

Fig. 3.1 Principle of quick return mechanism Fig.3.2 Quick Return Motion

The principle of quick return motion is illustrated in fig. when the link is in the position

PM, the ram will be at the extreme backward position of its stroke, and when it is at PN,

and the extreme forward position the ram will have been reached. PM and PN are

shown tangent to be crank pin circle. The forward cutting stroke, therefore, takes place

when the crank rotates to the angle C2L C1. It is evident that the angle C2K C1 made by

the forward or cutting stroke is greater than the angle C2L C1 described by the return

stroke. The angular velocity of the crank pin being constant the return stroke is,

therefore, completed within a shorter time for which known as quick return motion.

The ratio between the cutting time and the return time may be determined by the

formula:

Cutting time C2K C1

‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ = ‐‐‐‐‐‐‐‐‐‐‐‐‐

Return time C2L C1

Cutting time to return time ratio usually varies between 2:1 and the practical limit is 3:2

The only disadvantage lies with this mechanism is that the cutting speed and the return

speed is not constant throughout these stroke. It is minimum when the rocker arm is at

the two extremities and the speed is maximum when the rocker arm is vertical.

Q ‐2 what are the various shaper operations?

Ans‐ A shaper is a versatile machine tool primarily designed to generate a flat surface by

a single point cutting tool. But it may also be used to perform many other operations.

The different operations which a shaper can perform are as follows:‐

1) Machining horizontal surface. 2) Machining vertical surface. 3) Machining angular surface 4) Cutting slots, grooves, and keyways 5) Machining irregular surfaces





3rd

semeste

51

6) Machining splines or cutting gears.

Machining horizontal surface: ‐

Fig.3.3 Machining horizontal surface

Machining horizontal surface on a work piece. A shaper is mostly used to machine a flat,

true surface on a work piece held in a vise or other holding devices. After the work is

properly held on the table, a planning tool is set in the tool post with minimum

overhang. The table is raised till there is a clearance of 25 to 30 mm between tool and

the work piece. The length of stroke should be nearly 20 mm longer than the work and

the position of stroke is so adjusted that the tool begins to move from distance of 12 to

15 mm before the beginning of the cut and continues to move 5 to 8 mm after the end

of the cut. Proper cutting speed and feed is then adjusted. Short strokes should be given with slow speed. Both roughing and finishing cuts are performed to complete the job.

For roughing cut speed is decreased but feed and depth of cut increased. Depth cut is

adjusted by rotating the down feed screw of the tool head. The amount of depth of cut

is adjusted by a micrometer dial. The depth of cut for roughing work usually ranges from

1.5 to 3 mm while the finishing work it ranges from 0.075 to 0.200 mm. feed is adjusted





3rd

semeste

52

about one half the width of the cutting edge of the tool so that each cut will overlap the

last cut giving a smooth surface finish.

Machining vertical surface: ‐

Fig. 3.4 Machining vertical surface

1) Apron 2) work

Machining vertical surface on a work piece. A vertical cut is made while machining the

end of a work piece, squaring up a block or cutting shoulder. The work is mounted in the

vise or directly on the table and the surface to be machined is carefully aligned with the

axis of the ram. Aside cutting tool is set on the tool post and the position and length of

stroke is adjusted. The vertical slide is set exactly at zero position and the apron is

swiveled in a direction away from the surface being cut. This is necessary to enable the

tool to move upwards and away from the work during return stroke. This prevents the

side of the tool from dragging on the planed vertical surface during return stroke. The

down feed is given by rotating the down feed screw by hand. The feed is about 0.25 mm





3rd

semeste

53

Given at the end of each return stroke. Both roughing and finishing cuts are performed

to complete the job.

Machining angular surface: ‐

Fig. 3.5 Machining angular surface

1) Work 2) Apron 3) Swiveling angle

Machining of an angular surface on a work piece. An angular cut is made at any angle

other than a right angle to the horizontal or to the vertical plane. The work is set on the table and the vertical slide of the tool head is swiveled to the requires angle either

towards left or towards right from the vertical position. The apron is then further

swiveled away from the work so that the tool will clear the work during return stroke.

The down feed is given by rotating the down feed screw. Angular surface can also be

machined in a universal shaper or by using a universal vise without swiveling the tool

head.

Cutting slots, grooves, and keyways: ‐





3rd

semeste

54

Fig. 3.6 Cutting slots, grooves, and keyways

1) Vise 2) Tool 3) Work 1)Too bit 2) Work 3) Vise

With suitable tools a shaper can very congenitally machine slots or grooves on a work or

cut external keyways on shafts and internal key ways on pulleys or gears. For cutting

slots or keyways a square nose tool similar to a parting tool is selected illustrates cutting

of external keyways and cutting of internal keyways in shaper. External keyways are cut

on a shaft by first drilling ahole at the blind end of the keyways. The diameter of the

holes should be 0.5 to 0.8 mm oversize than the width of the keyway and the depth

should be about 1.5 mm larger than the depth of the keyway. This necessary to leave a

clearance on the tool at the end of the stroke. The length and position of stroke is

carefully adjusted so that the stroke will terminate exactly at the clearance hole. The speed is reduces while cutting a keyways. Internal keyway is cut by holding the tool on

special tool holder so that the tool post will not hit against the work at the end of the

stroke. The clapper block is locked in the clapper box to prevent the tool from lifting

during return stroke. Lubrication is necessary on the work to prevent the cutting edge of

the tool from wear due to dragging.

Machining irregular surfaces: ‐





3rd

semeste

55

Fig.3.7 Machining irregular surfaces

A shaper can also produce a contoured surface i.e. a convex or concave surface of

combination of any of the above surface. To produce a small contoured surface a

forming tool is used. If the curve is sufficiently large, power cross feed in conjunction

with a manual down feed is so adjusted that the tool will trace the required contour. If

the counter has too many ups and downs both the feeds are operated by hand. A round

nose tool is selected for machining irregular surfaces. For a shallow cut the apron may

be set the vertical but if the curve is quite sharp, the apron is swiveled towards right or

left away from the surface to be cut. Machining of a concave surface using a round nose

tool.

Machining splines or cutting gears:‐ By using and index centre, illustrated in gear or

equally, spaced spline may be cut. The work is mounted between two centers and spline

is cut similar to the cutting of a keyway. After the first spline is cut, the work is rotated

through a predetermined amount by using the index plate and index pin. The periphery

of a gear blank is divided, and equally spaced grooves are cut by using an index plate

having proper hole circles. While cutting gear a formed tool is used.

Q ‐3 Explain with neat sketch Whitworth quick return mechanism used in shaper?

Ans‐ Whit worth quick return mechanism is simple line diagram of the mechanism. The

bull gear mounted on large fixed pin upon which it is free to rotate. The crank plate 4 is

pivoted essentially upon the fixed pin at 5. Fitted on the face of the bull gear is the crank



NAGPUR

6

pin 2 o

provide

connectrotate a

circle o

point 5

will rota

movem

reciproc

but wh

been re

backwa

complet

position

time ta

return

T

closer o

position

Q ‐4 wh

Ans‐ Th

1) B2) C

INSTITUTE

the top

on the cr

s the crant a consta

a reduce

ith a vari

te in a circ

nt of the

ating of th

hen the p

n the pin i

ached. Wh

d position

ed when t

to the ba

en by the

otion is o

he length

r away fro

of pin 7 o

t are vari

different

ase

olumn

OF TECHNO

IG.3.8 Whi

of is mou

ank plate

plate by t speed th

2 and slid

ble angula

le and rota

ram simila

ram pass

in 2 is at th

at the po

en the pin

to the for

he pin 2 t

kward pos

crank pin

tained by

f stroke o

m the pivo

the ram.

us parts a

parts of a s

OGY

Question

tworth qui

ted the sl

. At the ot

pin 9 an crank pin

ing block

r velocity.

ry motion

to the cr

s through

e position

ition B, th

2 travels

ard positi

avels fro

ition. As th

to travel

he mecha

the ram

t 5. The p

d their fu

lotting ma

ank with s

ck return

iding bloc

er end of

the ram 2 with the

will caus

in 9 fitted

f the pin

nk and co

the pin 5 a

C the ram

extreme

rom C to

n in the c

B to C o

e angle vel

through a

ism.

ay be cha

sition of s

ctions of s

hine are:‐

olution

echanism

3. Slidin

the crank

8 by a pin sliding blo

the crank

on the oth

will be co

necting r

nd is norm

will be at e

orward po

the crank

tting strok

the pin 9

ocity of th

d an arc c

ged by sh

troke may

lotter mac

Manufacturi

block 3 f

late 4, a c

7. When bck 3 will r

plate to r

er end of t

nverted in

d mechani

l to the lin

xtreme ba

sition of th

pin 9 pas

e, and the

passes fr

crank pin

overing BD

ifting the p

be altered

ine?

g process‐I

ix into the

nnecting

ull gear witate on a

tate abou

e crank pl

o reciproc

sm. The a

e A5.

kward po

e ram will

es throug

return stro

m the for

is uniform

C. Thus a

osition of

by shiftin

3rd

semest

slot

od 6

ll be rank

t the

te 4

ting

is of

ition

have

the

ke is

ard

, the

uick

in 9

the



NAGPUR

7

3) S4) C5) R6) R7) R8) F

Base or

the ma

the sad

Column

houses

the colu

Saddle:

away fr

the wor

cross sli

Cross‐ s

moved

either b

Rotatin

cross sli

gear co

INSTITUTE

addle

ross‐ slide

otating ta

am and toam drive

eed mecha

Bed: ‐ the

hine. The

le is moun

: ‐ The col

riving me

mn is accu

‐ The sad

m the col

k. The top

e. These g

lide:‐ The

arallel to

hand or

table: ‐ T

de. The ta

nected to

OF TECHNO

le

l head assechanism

nism

FI

base is rigi

op of the

ted. The gu

mn is the

hanism of

ately finis

le is mou

mn either

face of the

uide ways

ross slide i

he face of

ower to su

he rotary t

le may b

the unders

OGY

Question

mbly

.3.9 main

ly built to

bed is accu

ide ways a

vertical m

the ram a

ed for pro

ted upon

by power

saddle is a

are perpen

s mounted

the colum

pply cross

ble is a ci

rotated b

ide of the

ank with s

parts of sl

take up all

rately finis

re perpen

mber whi

d feeding

iding way

he guide

r manual

ccurately fi

dicular to t

upon the

. The mov

eed.

cular tabl

y rotating

able. The

olution

tter.

the cuttin

hed to pro

icular to t

ch is cast i

echanism

on which t

ays and

ontrol to

nished to

he guide w

uide ways

ement of t

which is

a worm w

otation of

Manufacturi

forces an

vide guide

e column

ntegral wit

. The front

he ram reci

ay be mo

upply long

rovide gui

ays on the

of the sad

he slide m

ounted o

hich mesh

the table

g process‐I

d entire lo

ways on

ace.

h the base

vertical fa

procates.

ved towar

itudinal fe

de ways fo

base.

dle and m

y be contr

the top o

s with a

ay be eff

3rd

semest

d of

hich

and

ce of

s or

d to

r the

y be

olled

f the

orm

cted





3rd

semeste

59

against reservoir lever altering the direction of stroke of the piston and the cycle is thus

repeated.

Fig.3.10 hydraulic shaper mechanism.

The quick return motion is affected due to the difference in stroke volume of the

cylinder at both ends, the left hand end being smaller due to the presence of the piston

rod. As the pump is constant discharge one, within a fix period, the same amount oil will

be pumped into the right or to the left hand side of the cylinder. This will mean that the

same amount of oil will be packed within a smaller stroke volume causing the oil pressure to rise automatically and increasing the speed during the return stroke.

The length and position of stroke is adjusted by shifting the position of reversing dogs.

The cutting speed may be changed by controlling the throttle valve 3 which regulates

the flow of oil. When the throttle valve is partially closed the excess oil flows out

through the relief valve 11 to the reservoir maintain uniform pressure during cutting

stroke. A hydraulic shaper is now widely used for having many advantages.

Q ‐6 Explain

with

neat

sketches:

‐

Table feed mechanism in shaper

Ans‐ The automatic cross feed mechanism of the table is very simple. This is done by

rotating a ratchet wheel, mounted on cross feed screw C by the same amount each

time. This enables a corresponding equal rotation of the cross feed screw after each

stroke. The complete mechanism is as follows:



NAGPUR

0

It consis

and to t

to the l

about t

set ecce

which is

being e

turn, m

more t

moves t

power f

the retu

In som

compar

centre a

and vic

require

coarse f

INSTITUTE

Fig. 3.1

ts of slott

his is attac

ower end

e screw C

ntric with

driven by

centric wi

kes the ro

eth and t

he table.

ote, that t

eed to ope

rn stroke

latest typ

tively mor

ariation in nd the ce

versa. Th

on the jo

eed is nee

OF TECHNO

automati

d disc, whi

ed a conn

of the roc

, and at its

he slotted

the bull ge

h the disc

cker arm

us transm

he lower e

rate in eith

nly. If oth

es of shap

e efficient

the feed ctre of adju

amount o

b. For rou

ed. Agains

OGY

Question

table fee

ch carries

cting rod.

er arm o

upper en

disc centr

r. As the

centre, ca

o swing a

it an inter

nd of the

er directio

rwise the

ers, cam d

nd provid

n be provistable pin.

f feed to b

h machini

t this, a fin

ank with s

mechanis

T‐slot, in

The other

the pawl

carries a

. The slott

isc rotate

ses the c

out the sc

ittent m

awl is b

, but the

mechanis

riven feed

d a wider

ded by varLarger the

e given lar

ng heavier

r feed is e

olution

of a sha

this slot is

end of the

mechanis

spring loa

ed disc at i

through t

nnecting

rew C to

tion to th

veled on

ame shoul

will be su

mechanis

range of fe

ying the di set distan

gely depe

cuts are e

mployed in

Manufacturi

er.

fitted and

connecting

. The roc

ed pawl, a

ts back car

his gear th

od to reci

ove the p

e cross fe

ne side. T

d be set to

bjected to

are prov

eds.

stance R be greater

ds upon t

mployed a

finishing o

g process‐I

adjustable

rod is atta

er arm s

djustable

ries a spur

adjustabl

rocate. Th

wl over o

d screw

is facilitie

operate d

a severe st

ided whic

tween thill be the

e type of

nd therefo

perations.

3rd

semest

pin

ched

ings

in is

gear

e pin

is, in

e or

hich

the

ring

ress.

are

disc feed

inish

re, a





3rd

semeste

61

Q ‐7 Describes in brief the puncher slotters and tool room slotters.

Ans‐ Puncher slotters: ‐ Puncher slotters are heavy duty machines. Usually such jibs are

machined on these machines which are comparatively heavier and have been previously

brought roughly to the required shape through other operation like sawing, forging or stamping etc. the slotting machine is then used to cut of the surplus metal and finished

the work to the required shape and size. According to the nature of the work, either a

square or circular table can be fitted on the machine.

Tool room slotters: ‐ these slotting machines are precession type is used for accurate

machining. Usually titling type of frame is provided in these machines to enable

machining at different angles. Slotted link type drive is commonly used in these

machines. Rest of the construction is similar to that of a production slotter.

Q ‐8 State the function of the following parts of shaper.

Cross rail: ‐ The cross rail is mounted on the front vertical guide ways of the column. It

has to parallel guide ways on its top in the vertical plane that are perpendicular to the

ram axis. The table may be raised or lowered to accommodate different sizes of jobs by

rotating an elevating screw which causes the cross rail to slide up and down on the

vertical face of the column. A

Horizontal cross feed screw which is fitted within the cross rail and parallel to the top

guide ways of the cross rail actuates the table to move in cross wise direction.

Clapper box: ‐

The two vertical walls on the apron called clapper box houses the clapper block which is

connected to it by means of a hinge pin. The tool post of is mounted upon the clapper

block on the forward cutting stroke the clapper block feeds securely to the clapper box

to make a rigid tool support. On the return stroke a slight functional drag of the tool on the work lifts the block out of the clapper box a sufficient amount preventing the tool

cutting edge from the dragging and consequent wear.

Tool head: ‐ The tool head of a shaper holds the tool rigidly provides vertical and angle

feed movement of the tool and allows the tool to have and automatic relief during its

return stroke. The vertical slide of the tool head has a swivel base which is held on a





3rd

semeste

62

circular seat on the ram. The swivel base is graduated in degrees, so that the vertical

slide may be said perpendicular so the work surface or at any desired angle. By rotating

the down feed screw handle, the vertical slide carrying the tool executes down feed or

angle feed movement while machining vertical or angle surface. The amount of feed or depth of cut may be adjusted by of micrometer dial on the top of the down feed screw.

Apron consisting of clapper box, clapper block and tool post is clamped upon the vertical

slide by a screw. By releasing the clamping screw, the apron may be swiveled upon the

apron swivel pin either towards left or towards right with respect to the vertical slide.

This arrangement is necessary to provided relief to the tool while making vertical or

angle cuts. The two vertical walls on the apron called clapper box houses the clapper

block which is connected to it by means of a hinge pin. The tool post of is mounted upon

the clapper block on the forward cutting stroke the clapper block feeds securely to the

clapper box to make a rigid tool support. On the return stroke a slight functional drag of

the tool on the work lifts the block out of the clapper box a sufficient amount preventing

the tool cutting edge from the dragging and consequent wear. The work surface is also

prevented from any damage due to dragging illustrates the tool head of shaper.

Q ‐ 9 what are the various parts and their functions of shaper machine?

The working principle of shaper is illustrated in fig. in case of shaper, the job is rigidly

held in a suitable device like vice or clamp directly on the machine table. The tool is held

in a tool post mounted on the ram of the machine. This ram reciprocate to and fro and,

in doing so, makes the tool to cut the material in the forward stroke. No cutting of

material takes place during the return stroke of the ram. Hence, it is termed as idle

stroke. In case of draw cut shaper, the cutting takes place in the return stroke and the

forward stroke in an idle stroke. The job is given and the index feed (equal amount after

each cut) in a direction normal to the line of action of the cutting tool.

Principle part of a shaper:



NAGPUR

3

1) T

a) Bo

b) Cf

s

I

g

c) CT

p

r

j

d

t

d) T

INSTITUTE

able support

ase: ‐ it is

ther parts

olumn: ‐ It

r the ope

pport for

case of t

n its top i

uide ways

ross rail:‐

he cross ra

arallel gui

m axis. T

bs by rot

own on th

orizontal c

p guide w

able:‐

OF TECHNO

Fig.3.

2) Table 3) Cl

a heavy an

f the mac

is a box ty

ating mec

other parts

e hydrauli

carries m

t its front.

il is mount

e ways on

e table ma

ting an el

vertical fa

ross feed s

ays of the

OGY

Question

12 parts o

apper box 4)

d robust c

ine which

e cast iro

anism of

of the ma

shaper, it

chined w

d on the f

its top in

y be raise

vating scr

ce of the c

crew whic

ross rail ac

ank with s

a shaper

Apron Clam

st iron bo

are mount

body mou

he machin

hine such

carries th

ys, in whi

ront vertic

he vertica

or lower

w which

lumn.

is fitted w

tuates the

olution

ing bolts 5)

y which a

ed over it.

nted on th

e and the

as cross rai

hydraulic

h the ram

l guide wa

l plane tha

d to acco

auses the

ithin the c

table to m

Manufacturi

down feed h

ts as a su

e base and

electrical.

l and ram.

drive mec

reciprocat

ys of the c

t are perp

modate d

cross rail

oss rail an

ve in cros

g process‐I

nd wheel

port for al

acts as ho

It also acts

tc.

anism insi

es, and ve

lumn. It h

ndicular t

ifferent siz

to slide up

parallel t

wise direc

3rd

semest

l the

sing

as a

e it.

tical

as to

the

es of

and

the

tion.





3rd

semeste

64

It is made of cast iron and has a box type construction. It holds and supports the

work during the operation and slides along the cross rail to provide feed to the

work. T slot are provided on its top and sides for securing the work to it

.

e) Ram:‐It is also an iron casting, semicircular in shape and provided with rib construction

in side for rigidity and strength. It carries the tool head and travels in dovetail

guide ways to provide a straight line motion to the tool. It carries the mechanism

for adjustment of ram position in side it.

f) Tool head: ‐The tool head of a shaper holds the tool rigidly provides vertical and angle feed

movement of the tool and allows the tool to have and automatic relief during its

return stroke. The vertical slide of the tool head has a swivel base which is held

on a circular seat on the ram. The swivel base is graduated in degrees, so that the

vertical slide may be said perpendicular so the work surface or at any desired

angle. By rotating the down feed screw handle, the vertical slide carrying the tool

executes down feed or angle feed movement while machining vertical or angle

surface. The amount of feed or depth of cut may be adjusted by of micrometer

dial on the top of the down feed screw. Apron consisting of clapper box, clapper

block and tool post is clamped upon the vertical slide by a screw. By releasing the

clamping screw, the apron may be swiveled upon the apron swivel pin either

towards left or towards right with respect to the vertical slide. This arrangement

is necessary to provided relief to the tool while making vertical or angle cuts. The

two vertical walls on the apron called clapper box houses the clapper block which

is connected to it by means of a hinge pin. The tool post of is mounted upon the

clapper block on the forward cutting stroke the clapper block feeds securely to

the clapper box to make a rigid tool support. On the return stroke a slight

functional drag of the tool on the work lifts the block out of the clapper box a sufficient amount preventing the tool cutting edge from the dragging and

consequent wear. The work surface is also prevented from any damage due to

dragging illustrates the tool head of shaper.





3rd

semeste

65

g) Vice:‐It is a job holding device and is mounted on the table. It holds and supports the

work during the operation. Alternately, the job can be directly clamped to the

machine table.

MILLING MACHINE AND IT’S OPERATIONS:‐





3rd

semeste

66

UNIT‐IV

Q ‐1 Explain with a neat sketch Universal Milling Machine.



NAGPUR

7

Univers

adopte

distingu

is mounswivelle

can be

spindle.

incorpo

is fed a

helical

milling

increas

milling

produc

all conv

every t

univers

very acc

Table 2

movem

connect

wheel

INSTITUTE

l Milling

to a very

ished from

ted on a cid to any a

wivelled a

Thus in

ated in a

t an angle

illing ope

ttachmen

d by the u

attachmen

spur, spir

ntional m

pe of op

l machine

urate wor

. Hand w

nt 4. Tabl

ions 7. M

or longitu

OF TECHNO

achine: A

wide rang

a plain mil

cular swivgle up to

bout is ve

universa

lain millin

to the mil

ation whic

is used. T

e of speci

t, rotary

l, bevel ge

illing opera

rations th

is, therefo

.

Fig 4.1 Un

heel for s

e stop 5.

tor for au

dinal feed

OGY

Question

universal

of milling

ling machi

lling base 5 degree

tical axis

l milling

machine,

ling cutter

cannot b

he capacit

l attachme

ttachment

ars, twist d

tion. It ma

t can be

e, essenti

iversal mill

election o

and whe

omatic fe

10. Over

ank with s

illing ma

operation

e in that t

hich has n either s

nd set an

achine, i

the table

. This addi

done on

of a univ

nts such a

, slotting

rills, ream

also be e

performed

lly a tool r

ing machin

f spindle

l for feed

d 8. Leve

an 11. C

olution

hine is so

. A univer

he table o

egree graide of the

angle oth

addition

ay have a

tional feat

plain milli

ersal millin

dividing h

attachmen

rs, milling

mployed

on a sha

oom mach

e

3. Adjusta

selection

for vertic

ver for

Manufacturi

named be

al milling

universal

ations andormal pos

r than rig

to three

fourth mo

ure enable

ng machin

g machine

ead or ind

t, etc. Th

cutters, et

ith advant

er or on

ine design

ble stop

. Terminal

l and cro

ain drive

g process‐I

ause it m

achine ca

illing ma

the tale cition. The

t angles t

movemen

ement wh

s it to per

unless a

is conside

x head, ve

machine

. besides

ge for an

a drill pre

d to prod

or longitu

box for

s feed 9.

12. Arbo

3rd

semest

y be

n be

hine

n be able

the

s as

en it

form

piral

ably

tical

can

oing

and

s. A

ce a

dinal

ains

and

13.





3rd

semeste

68

Longitudinal feed changing lever 14. Hand wheel for cross travene 15. Handle for

vertical traverse of knee 16. Base.

Q ‐2 Name the various types of cutters used in milling operation. Sketch a Plain milling

cutter showing its elements.

Common type of milling cutters is the following:

1. Plain milling cutters 2. Side milling cutters 3. End milling cutters 4. Face milling cutters 5. Metal Slitting cutters (Slitting saws) 6. Angle milling cutters 7. Formed milling cutters 8. Woodruff ‐key milling cutters 9. T‐slot milling cutters 10. Fly cutters

Plain milling cutters

These milling cutters may have the cutting teeth on their periphery. The teeth may be

either straight, i.e., parallel to the axis, or helical. Their end faces are either ground

square with the axis or slightly concave to reduce friction. Thus no cutting action is

provided by the side faces. These cutters are employed for milling flat surfaces parallel

to the axis of rotation.



NAGPUR

9

1.) and up to 2

sot cutt

teeth. T

cutters

called h

carry le

very he

with les

at all ve

up with

left han

Side Mil

cutting

INSTITUTE

Fig

These cu

he helical mm in wi

ing. The la

hese cutte

are used f

avy duty s

s number

vy cuts ar

power co

ry big leng

a number

to neutra

ling Cutter

eeth on o

OF TECHNO

.2 Plain m

tters inclu

or slab milth and ca

ter type, i.

s are mad

r light wo

lab milling

Fig 4.

of teeth, h

to be em

nsumption.

h is neede

of short le

lize the en

s: These cu

e or both

OGY

Question

illing cutte

e the light

ling cutterries straig

e., slab mi

to have e

rk and fini

cutters. Th

4 Fine heli

aving a ste

ployed, sin

A recomm

, a prefer

ngth cutte

thrust.

tters, apar

ides. They

ank with s

Fig 4.3

duty plain

(Fig 2. ant teeth. It

lling cutte

ither fine

shing wor

ey

al teeth sl

ep helix a

ce they ar

ended pra

ble practi

s with the

t from havi

are alway

olution

Coarse hel

milling cut

Fig 3.). Tis usually e

s are eno

itch or co

. The coar

b mill

gle. They

capable

ctice is not

e is to ha

ir teeth ru

ng teeth o

provided

Manufacturi

ical teeth s

ter or key

e former tmployed f

gh long a

rse pitch.

se pitch te

re commo

f removin

to use ver

ve the desi

ning alter

n the peri

with a cen

g process‐I

lab mill

ary cutte

ype is avair key war

d carry h

ine pitch t

eth cutter

nly used w

more ma

long cutt

red length

ately righ

hery, also

ral hole fo

3rd

semest

(Fig

lable and

lical

eeth

are

here

erial

rs. If

built

and

have

r the



NAGPUR

0

purpose

in pairs.

1. P

a

sl

c

d

2. si

hp

fi

l

l

o

3. S

p

sit

T

o

4. I

t

INSTITUTE

of mounti

The main

lain side m

s well as o

ots or in f

utters are

iameters u

alf side mi

de only. T

elical. Alsoerformed

nishing an

nger than

ft hand a

peration b

taggered t

eriphery o

de to side,en on the

hey prove

f staggere

terlocking

illing cutt

at their te

OF TECHNO

ng them o

ypes of sid

illing cutte

n both sid

ce milling.

available

p to 200 m

Fig 4. 5

lling cutte

ey can be

they can by teeth

sizing wo

those of p

d one rig

ing know

eeth side

ly. These

just as thother. Th

very efficie

tooth sid

side milli

rs but are

eth interlo

OGY

Question

the arbo

e milling c

rs. They a

es, as sho

They can

in differen

m.

tandard o

s. These c

used for f

e either rirovided o

k. A distin

lain milling

t hand) fo

as straddl

illing cutt

alternate t

teeth of y are com

nt in millin

milling cu

g cutters.

sed as uni

ck, as sho

ank with s

. They are

tters are t

e made to

n in fig 4

also be us

t widths r

r plain side

utters hav

ce milling.

ght hand n the peri

t feature

cutters. T

r milling t

milling.

ers. These

eth are o

ood saw, only use

g deep slo

ter is sho

These cu

t, consistin

n in Fig 4.

olution

also calle

e followin

have cutti

. They are

d in pairs

anging fro

milling cut

teeth on

The teeth

r left hanphery whi

f these cu

ey are fre

o parallel

cutters ca

opposite

nd cut alt for keyw

ts but narr

n in Fig 4.

tters are

g of two c

They can

Manufacturi

straddle

g:

ng teeth o

normally

for straddl

m 5 mm

ters

the periph

may be ei

. Actual cule the sid

ters is tha

quently us

surfaces s

rry alterna

elix angle,

rnatively y cutting a

ow in widt

imilar in

tters joine

be adjuste

g process‐I

ills when

the peri

sed for cu

milling. T

o 25 mm

ery and o

ther straig

tting oper teeth do

their teet

d in pairs

imultaneo

te teeth i

staggered

n one sidnd slot cu

. A typical

esign the

d together

to acquir

3rd

semest

used

hery

tting

hese

and

the

t or

tion the

are

(one

sly ;

the

from

and ting.

one

side

such

the



NAGPUR

1

r

s

r

Fig 4.

5. E

t

t

c

f

r

o

1

2

INSTITUTE

quired wi

acers are

ear and f

latively wi

Staggere

nd milling

o differe

e shank.

ay be str

utters. Heli

r milling s

ills may h

nge of di

ounted di

r in an ada

. Commo

and also

howeve

this type

. Two‐lipp

These c

OF TECHNO

dth by ins

also used

equent sh

der slots t

teeth side

cutters: T

t varieties;

hey carry

ight i.e., p

cal teeth

lots, keyw

ave either

ameters fr

ectly on t

ptor. The f

type. The

on the en

, available

is shown i

Fig 4.

ed end mi

tters hav

OGY

Question

erting shi

o make go

rpening o

exact wid

milling cu

hese are s

those hav

eeth on t

arallel to t

ay be righ

ys, groove

taper sha

om 3 mm

e spindle

llowing ar

se milling

. The teet

in small siz

Fig 7.

8 Commo

ll. These

two strai

ank with s

s or spac

od the red

f the teet

h. Also, th

ters Fig

lid circula

ing the sha

e periphe

he axis of

t hand or l

s and irre

k or strai

to 50 m

r held in c

the main

cutters ca

h may be s

es only, sa

type end

illing cutt

ht or heli

olution

ers betwe

uction in

. These c

y find a wi

4.7. Interl

r cutters

nk and the

y as well a

rotation, o

ft hand. E

ular shape

ht shank

. Shank t

ollets (stra

classificati

ry multipl

traight or

below 8

illing cutt

rs are als

cal teeth

Manufacturi

n them.

idth of th

tters are

de use in g

cking side

hich are

others wh

s on the e

r helical a

d milling

surfaces.

and are a

pe end

ight shank

n of these

teeth on

elical; the

m dia. A t

er

known a

n the per

g process‐I

hese shi

cutters d

sed for m

ang milling

milling cut

anufactur

ich do not

d. These t

in slab m

utters are

hank type

ailable in

ills are e

type mills

end mills:

their perip

former ty

ypical desi

s slotting

iphery an

3rd

semest

s or

e to

illing

.

ters.

d in

have

eeth

illing

used

end

wide

ither

nly)

hery

e is,

n of

ills.

the



NAGPUR

2

3

INSTITUTE

correspo

advanta

drill and

depth. cutters

howeve

. Shell en

the othe

both. Ge

these cu

stub arb

which e

teeth ar

These cu

the end by them

shown i

OF TECHNO

nding two

e of these

then fed l

lso, they ay have

, more co

Fig 4.

milling c

r types of

nerally the

tters provi

or, shown

gage the

provided

tters are e

or face, an. The form

Fig 9.

OGY

Question

teeth on t

cutters is t

ongitudina

an be usither a st

monly use

9. Two‐lip

tters. The

end mills.

y are mad

ed with a

in Fig. 4.9.

ollar keys

on these c

ployed fo

cutting sler operati

ig 4.10 Sh

ank with s

e end, whi

hat they ca

lly to pro

d for takiaight sha

d (see Fig

ed taper s

se cutters

They have

in over 5

recess to r

Two slots

of the arb

utters. Th

r heavy du

ots, etc. arn is calle

ll end milli

olution

ch meet a

n be fed st

uce a gro

ng heavy k or taper

.9.)

hank end

are larger

teeth on t

mm size (

ceive a ca

are made

r to get t

se teeth

ty work. M

the com facing. A

ng cutters.

Manufacturi

the end c

raight into

ve of desi

uts in soli shank. Th

illing cutt

and heavi

he periphe

iameter).

screw. Th

across the

e drive.

ay be righ

illing of fla

on operatshell end

g process‐I

ntre. The

the metal l

red length

d stock. Te latter ty

r.

r than mo

ry and the

The end fa

ey are hel

back of c

enerally h

and left

surfaces,

ions perfoilling cut

3rd

semest

ain

ike a

and

hese pe is

st of

end

ce of

in a

tter,

lical

and.

sing

med er is



NAGPUR

3

Face mi

almost

(See Fig

cutting finishin

consists

Fig 11).

The she

directly

Fig

Metal sl

are use

followin

1

INSTITUTE

lling cutte

esembles

10). It ca

is done by operatio

of a steel

The forme

ll type cutt

on the spi

4.11 Shell‐

itting cutt

for cuttin

g two vari

. Plain sli

compar

some si

widths,

is shown

OF TECHNO

s: These c

shell end

rries teeth

the teeth . The larg

ody, alon

r type is u

er is usuall

dle nose.

ype face m

rs: These

g thin slot

ties:

ting saws.

d to othe

e relief i

anging bet

in Fig 4.13

OGY

Question

tters are

milling cut

on the p

periphery r type of

the perip

sed for sm

y held in a

illing cutte

cutters are

for partin

They are

types of

order to

ween appr

ank with s

made in t

er and is k

riphery as

and thosecutter, cal

ery of whi

all work w

slub arbor

r Fig

also frequ

g off. The

plain mill

milling cu

prevent r

oximately

olution

o commo

own as Sh

well as t

on the eled the b

ch are inse

hereas the

and the la

4.12 Built‐

ently calle

are com

ing cutter

ters. Thei

bbing. Th

1 mm and

Manufacturi

forms. T

ell‐type fa

e end of

d face peilt‐up face

rted the cu

latter for

rger type c

p type fac

metal slit

only manu

which a

teeth are

ey are ma

5 mm. A p

g process‐I

e smaller

e milling c

ace. Maxi

form a ty milling cu

tting teeth

larger surf

an be mou

e milling cu

ting saws.

factured i

e very thi

provided

de in diff

lain slitting

3rd

semest

type

tter

um

e of tter,

(see

ces.

nted

tter

They

the

n as

with

rent

saw



NAGPUR

4

2

Angle m

These c

axes. Th

other a

1. S

t

t

2. c

t

n

INSTITUTE

. Staggere

heavier

teeth al

generall

illing cutte

tters carr

eir specific

gular surf

ingle angle

e angular

illing of beth may h

Double‐

utters in th

eth. The i

ecessary t

OF TECHNO

Fig 4.

d teeth mi

work. The

o, similar

made in d

rs

sharp an

use is in

ces. The fo

cutters (Fi

face or on

oth the flaave an incl

Fig 4.14

ngle cutte

at they ha

ncluded an

at the fac

OGY

Question

13 Metal

lling cutte

have the

o the stag

ifferent wi

ular teeth

illing V‐gr

llowing tw

. 4.14). T

oth, the a

nks of the ded angle

ingle angl

rs (Fig. 4.

e two ang

gle of this

s should b

ank with s

litting saw.

(saw). Th

ir teeth st

gered teet

ths rangin

which are

oves, not

types of

ese cutter

ngular face

included of 45 or 6

cutter

5). These

ular faces

‘V’ is eith

equal.

olution

se saws a

aggered al

h side milli

g from 4 m

neither p

hes, dovet

ngle cutte

may have

and the si

ngular gro degree.

Fig 4.15

cutters di

hich join

r 45, 60, 9

Manufacturi

re used fo

ternatively

ng cutter.

m and 10

rallel nor

ail slots, re

s are in co

their teet

e. The latt

ove simult

ouble angl

fer from t

ogether to

0 degree,

g process‐I

comparat

and have

These saw

m.

normal to

amer teet

mmon use:

either on

er type en

aneously;

e cutter

he single

form V‐sh

hough it i

3rd

semest

ively

side

are

their

and

ly on

bles

heir

ngle

ped

not



NAGPUR

5

Form m

cutters.

differen

their focommo

1

2

INSTITUTE

illing cutt

This categ

t shaped c

rm and si types of f

. Corner rcorners

single cu

left han

hand an

Fig 4.

rou

. Concave

form reli

circular

should t

to the c

the sha

used for

concave

OF TECHNO

rs: They a

ry include

unters. Th

e are retorm reliev

ounding c

f the jobs

tters or do

(Fig. 16).

left hand

16 R.H. Co

nding cutt

and conv

ved cutter

ontours of

erefore, b

tters, do

e and the

milling to

surface.

OGY

Question

re also kn

s a fairly la

eir teeth a

ined evend cutters:

tters:‐ Th

to a requir

uble cutte

he double

in a single

ner Fig

r Corne

cutt

x cutters:‐

. They are

half circle

e carefully

ot indicat

cutter tee

convex su

ank with s

wn as fo

rge variety

e provide

after res

se cutter

ed radius.

rs. Single c

cutter (Fig

nit.

.17 L.H.

rounding

er

These cutt

used for m

or less. Th

noted that

the shap

th. As suc

face and

olution

m relieve

of milling

with a ce

arpeninn

are used

hey are m

utters may

. 17) has a

Fig 4.

ers are ver

illing conv

above na

the name

e of the s

a concav

onvex cut

Manufacturi

milling c

utters use

tain angle

. The fol

for milling

anufactur

be right h

combinati

8. Double

y common

x and con

es somet

concave

rface to b

e cutter (F

er (Fig 4.2

g process‐I

tters or r

d for prod

of relief so

lowing ar

the edges

d separat

and (Fig. 1

n of both

rounding c

ly used typ

ave surfac

imes misle

r convex,

produce

ig 4.19) wi

0) for milli

3rd

semest

dius

cing

that

the

and

ly as

5) or

right

tter

es of

es or

d. It

iven

but

ll be

ng a



NAGPUR

6

3

4

5

6

INSTITUTE

. Gear cutfor milli

roughin

Fi

. Tap and

reamers

that thei

reamer

. Gear Hocutting

operatio

spine sh. Thread

different

cutters

will corr

have alr

OF TECHNO

Fig.

ters:‐ They

g gear te

and finishi

4.21. A f

cutte

reamer fl

and taps.

r two incli

luting cutt

bs:‐ A gear

eeth on it

ns, such as

fts, etc. A milling cu

types of t

an be sing

espond to

ady been

OGY

Question

.19 A conc

are also d

th on a

ng, shown

rm relieve

r (roughin

ting cutte

In appear

ed faces m

r is shown

hob is a f

s peripher

cutting te

tandard f ters:‐ The

hreads, m

le or multi

the angle

escribed i

ank with s

ve cutters

esigned as

illing ma

in Fig. 4.2

d gear

)

s:‐ These

nce, they

eet to for

in Fig 4.23

rmed milli

. It is us

th of wor

rm of suchse are al

stly for w

‐teeth. Th

of the thr

detail in

olution

Fig.

inviolate g

hine. The

and Fig. 4.

Fig 4.22 A

cutte

ormed are

look like

a rounde

ng cutter

d for a n

wheels,

a cutter is o formed

orms and

included

eads to b

rt. 12.23

Manufacturi

4.20 A con

ear cutters

two com

22 respect

orm reliev

r (finishing

used for

ouble angl

d corner. A

hich cutte

mber of

helical and

shown in Fcutters u

acme type

angle of th

produced

g process‐I

vex cutter

. They are

on grade

ively.

d gear

illing flut

e cutters,

typical ta

r carries h

ifferent m

spur gear

ig 4.24 ed for m

threads. T

e cutting t

. These cu

3rd

semest

used

are

s on

such

and

lical

illing

and

illing

hese

eeth

tters



NAGPUR

7

Woodr

It is a ssizes sa

machin

same o

sides h

both on

shown i

T‐

Slot‐

slots. In

Fig 4.26

groove

slot‐mill

provide

the cutt

INSTITUTE

Fig 4.2

ff ‐key mill

all type o up to 5

spindle,

an arbor.

ving a littl

the perip

Fig. 4.25

illing

Cuttsmaller si

Large size

t the top i

ing cutter

between

er through

OF TECHNO

3 Tap and

ing cutter:

end millin mm dia

hereas th

Smaller siz

e clearanc

ery as we

Fi

er:‐

It is aes it is ma

cutters ar

s first mill

is then e

the shank

the upper

OGY

Question

eamer flut

g cutter weter, are

e larger si

es generall

. Larger s

ll as the si

4.25 Wo

single ope to have

mounted

d by mea

ployed fo

and the c

roove as t

ank with s

ing cutters

ich resemmade to h

es are pr

y have str

izes are us

des. A sm

druff ‐key

ration cutthe shank

on a sepa

s of slottin

milling th

tter. It fa

he cut pro

olution

Fig 4.24

les with pave solid

vided wit

ight teeth

ually mad

ll size wo

illing cutt

ter which iintegral wi

rate shank

g cutter o

e wider g

ilitates an

eeds.

Manufacturi

ear Hobs

lain and sihank, to

a hole fo

on the per

to have

druff ‐key

r

s used onlth the cutt

. In operati

end millin

oove. Not

unhindere

g process‐I

e mills. Sme fitted i

r mountin

iphery wit

taggered t

illing cut

y for cuttier, as sho

on, the na

g cutter. T

the thin

moveme

3rd

semest

aller the

the

the

eeth

er is

g T‐n in

rrow

e T‐

neck

nt of



NAGPUR

8

Fly cutt

held in

Screws

tool can

generall

capable

Angles

A millin

tools, s

Before

cutter t

and the

angles

which isthe reli

the axis

influenc

friction

life bet

a conse

relief an

face of

facilitat

consum

consequ

increas

the tool

INSTITUTE

r: ‐ It is a

stub arbo

are used f

be groun

y used for

of produci

f a plain

cutter ca

ch that ea

roceeding

eth, such

depth are

f a plain

normal to ved land o

of the cu

e the sele

and hence

een two g

quent redu

gles betwe

the cutter

s free cutt

ption of

ently a gr

d beyond

.

OF TECHNO

ctually a si

r or held in

r tightly h

to any de

experime

g a very a

illing cutt

be consi

ch tooth o

on to the

as face, cu

the principl

illing cutt

the axial pf the cutte

ter. Due c

tion of a

the wear

rinds and

ction in th

en 10 and

The rake

tooth, me

ing by the

ower, be

ater life o

0 degree

OGY

Question

Fig 4.26

ngle point

a bar, exa

olding the

sired shap

tal purpos

curate sur

r:‐

ered as a

the cutter

tudy of to

ting edge,

es dimensi

r. The reli

lane PP at r tooth. Th

onsiderati

roper reli

n the land

nsure a be

e lip angle

0 degree.

ngle (γ) is

sured in a

ool by allo

ter surfa

the tool

therwise

ank with s

T‐slot‐mill

tool. It is

ctly in the

tool in th

. It can, t

es since s

faces.

uilt up un

is a single

l angles, n

back, flute

ons of the

f angle (o

a point, onis angle is

n must b

f angle. H

. Also a lar

tter surfac

(β), it will

the angle

plane no

wing the c

e finish,

etween t

he resultin

olution

ing cutter

ither mou

ame way

above ho

us consid

ch a cutt

it of a num

point cutti

ote the na

, fillet, lan

cutter teet

) is the a

the cuttineasured i

given to

igher the

ger relief a

e finish, bu

make the

between t

mal to th

ip to flow

less wear

o grinds.

g smaller l

Manufacturi

nted on a

s a boring

lders. Cutti

red as a f

r, if prope

ber of sing

ng tool, as

es of vari

, etc.., To

h. represe

gle betwe

edge, ann a plane p

the variou

alue of thi

ngle will i

t at the sa

tooth wea

he axial pl

cutting e

smoothy.

on the t

owever, i

ip angle wi

g process‐I

ylindrical

in a boring

ng edge o

rmed tool.

rly design

le point cu

shown by ‘

us parts o

th thickne

ts the diff

n the plai

the tangeerpendicul

s factors

s lesser wi

crease the

e time, d

k, normall

ne PP an

ge. Rake

his ensure

ooth face

should n

ll again we

3rd

semest

ody

bar.

f the

It is

d, is

tting

A’ in

f the

s ‘T’

rent

P1,

nt to ar to

hich

ll be

tool

e to

the

the

ngle

less

and

t be

aken



NAGPUR

9

called li

lip angl

feasible,particul

employ

and 50

Q ‐3 Diff

Milling

means

is the s

that ea

This all

Obvious

cylindri

operati

1. d

2. c

INSTITUTE

angle (β).

conserve

taking intrly impor

d. Cutters

egree. Th

erentiate

ethods:

f a multi‐t

me as tha

h tooth, a

ws the to

ly, minimi

al cutters,

n:

p or conv

irection op

own or cli

oincides wi

The abo

noted at

OF TECHNO

The angle

Its value

a stronge

considerant while

having he

recomme

etween U

illing, as

eeth rotati

of a singl

ter taking

oth to coo

es the eff

the follow

entional m

posite to t

mb millin

th directio

Fig. 4.27 C

e relative

the point

OGY

Question

between

epends up

tooth. As

tion the familling ha

lical teeth

ded value

Milling a

as alread

g tool, cal

point tool

cut, comes

l down b

ct of heat

ing two m

illing. In t

at in whic

. In this

of work f

onvention

irections

of contact

ank with s

the face a

on the val

such, end

ctors explrder metal

are made

of principl

d Down

been sta

led cutter.

. However

in operati

fore the n

developed

thods are

his metho

the work

ethod th

ed, as sho

l milling

f moveme

between

olution

nd the la

es of rake

avor shoul

in in the f s and wh

to contain

s angles a

illing.

ed, is a p

The form

, an impor

on again a

ext cuttin

in cutting

commonl

of millin

is fed [see

direction

wn in Fig 2

Fig. 4.28

nts of the

the two. O

Manufacturi

d of the

and relief

d be to ke

rgoing pan deeper

a helix an

re given in

ocess of

f each too

ant featur

ter some i

operatio

on the cut

used for

g the cutt

Fig 1].

of rotatio

.

Climb milli

cutter and

n compari

g process‐I

utter too

angles. A l

p it as lar

agraphs. Tcuts are t

le betwee

able 1.

etal cutti

th of the c

to be not

nterval of

is done

ting edge.

performing

er rotates

of the c

ng

work shoul

g Figs 1 a

3rd

semest

th is

rger

e as

is is o be

n 10

g by

tter

ed is

ime.

y it.

With

this

in a

tter

d be

nd 2





3rd

semeste

80

you will find that the shape of chip (shaded area between points A and B)

removed by the cutter in both the cases is same, but an difference is that in

conventional milling, as the cut proceeds, the chip thickness increases

gradually; as from A to B. Against this, the chip thickness decreases in case of climb milling. In other words we can say that the chip thickness in

conventional milling is minimum (zero) at the start of cut and maximum at the

end of the cut, whereas in climb or down milling. It is a reverse case, i.e.,

maximum in beginning and zero at the end.

The selection of a particular method, of the above two,

depends upon the nature of work. The former method, i.e., conventional

milling is commonly used for machining castings and forgings since this

method enables the cutter to dig‐in and start the cut below the hard upper

surface. The second method i.e., climb milling is particularly useful for

finishing operations and small work, such as slot cutting, milling grooves,

slitting, etc. It gives a better surface finish but it should be ensured, before

employing this method, that there is no backlash in the feeding mechanism of

the table and the work is rigidly held.

Q ‐4 writes short notes on:

i) Milling machine specification:

Size and specifications: Size of milling machine is usually denoted by the

dimensions (length and breadth) of the table of the machine. Different

manufactures, however, these sizes by different numbers 0, 1, 2, 3, 4, 5, 6,

etc. Each of these indicates a particular standard size adopted by the

manufacturer and the relative literature from the manufacturer should be

thoroughly consulted before for a particular number. The corresponding

dimensions to a particular should be known before ordering for it so that it

can meet the requirement. Other main specifications of the machine to be

considered at the time of orders are the horse power of driving motor,

number of spindle. Speeds, drive, taper of spindle nose, required floor

area, gross weight, etc.



NAGPUR

2

ii

INSTITUTE

i) Diffe

Milli

auxili

comrang

milli

cutte

used

Verti

used

on t

attac

With

mach

point

cann

to b

adva

verti

to m

OF TECHNO

ent attach

g machin

ary device

onents of versatilit

g machin

r by alteri

for positio

al milling

both on h

e machin

hment bol

the use

ine can b

, which ne

t be adjus

adjusted

tageous f

al plane, t

chine an i

OGY

Question

ment of m

attachme

intended

the millin, producti

attachm

g the cut

ing, holdi

attachmen

rizontal a

e the ove

ed on to t

f this att

made to

eds attent

ted in a ve

by raisin

ature tha

make the

clined sur

Fig 4.3

ank with s

illing mach

nts‐ The

to be fast

machine ity or acc

nts are u

er axis an

g and feed

t: It is als

well as u

r‐arm of

e front fa

achment t

act as ver

ion here, i

tical direct

g the tab

t it can b

spindle an

ace on the

Vertical

olution

ine:

ttachment

ened to or

for the puracy of o

ed for po

d speed,

ing.

sometim

iversal mi

he latter

ce of the c

he horizo

ical millin

s that the

ion. As suc

le of the

swivelled

d hence th

work‐piec

illing attac

Manufacturi

s are stan

joined wi

rpose of peration. S

sitioning

hereas ot

s called s

lling machi

is pushed

olumn, as

tal and u

machine

universal

h, the dept

machine.

to a desi

cutter, ro

.

hment

g process‐I

ard or sp

h one or

ugmentinome class

nd driving

her classe

ivel head.

ne. For fixi

back and

hown in F

niversal m

. An impo

illing ma

h of cut ha

But it ha

red angle,

tate at an

3rd

semest

ecial

ore

the s of

the

are

It is

ng it

the

ig. 2.

illing

rtant

hine

s got

s an

in a

ngle



NAGPUR

3

For pro

horizon

through

the verunivers

attachm

Operati

this atta

Spiral m

can be

adjuste

spindle

article. I

a surfac

Slotting

keyway

perform

machin

used fo

column

mechan

motion

the fron

INSTITUTE

iding the

al spindle

a train of

ical spindll milling m

ent, still i

ns like fa

chment.

illing atta

swivelled

at any de

exactly in t

t thus pro

e on the w

attachme

cutting, gr

ed, but th

. In such

this purp

in the sa

ism which

of the ram

t of the att

OF TECHNO

rive to ve

f the mac

spur gears

e. It may, achines ca

t will not

e milling,

hment: Th

in two pla

sired inclin

he same w

ides a gre

rk withou

t: In mac

ooving, slo

e bulk of

ases the

se. This at

e way as

converts t

of this att

achment. I

OGY

Question

tical spind

ine. It driv

and finally

however, n be conve

be as ef

rooving, T

is is a univ

nes. This

ation in tw

ay as in a

t flexibility

disturbing

ine shops

tting, and

work may

illing ma

tachment (

a vertical

e rotary m

achment.

carries th

ank with s

le of the a

es a horizo

a pair of b

e noted trted into v

ficient as

‐slot cuttin

ersal type

enables th

o differen

ertical mil

to adjust

the settin

, simple sl

internal g

not justif

hine, fitte

Fig 3) is fi

illing atta

otion of th

slide or

slotting t

olution

tachment

ntal spindl

evel gears

hat even tertical mill

a regular

g, etc. can

of vertical

e spindle

planes. T

ling attach

he cutter i

of the wo

otting ma

ar cutting,

the exist

with a sl

ted to the

chment. It

e machine

am works

ol.

Manufacturi

an adapte

e in the att

the drive i

hough the ing machin

vertical m

easily be

milling att

of the att

e drive is

ment desc

n any posi

rk.

hine oper

etc., may

ence of s

otting atta

front face

s body car

spindle in

in the guid

g process‐I

is fitted t

achment.

transmitt

horizontales by usin

illing mac

erformed

achment

chment t

btained b

ibed in th

ion to ma

ations, su

be requir

parate slo

chment ca

of the ma

ries an int

o reciproc

es provide

3rd

semest

the

hen,

d to

and this

hine.

with

hich

o be

the

last

hine

h as

d to

tting

n be

hine

rnal

ting

d on





3rd

semeste

84

Fig 4.31 A Slotting attachment

Rack milling attachment: This attachment is used for cutting teeth in racks. It can also be

employed, conjunction with the universal dividing head, for cutting worm, It is mounted

on the machine column and cutter is mounted on the arbor provided in this attachment.

The arbor means parallel to the longitudinal traverse of the machine table on which the

work piece is held for cutting the teeth.

Q ‐5 Give the classification of milling machine.

Types of milling machine: A large variety of different types of milling machines is

available and it is really difficult to account for all these types in this small chapter. The

broad classification of these machines can be done as follows:

1. Column and knee type milling machines, 2. Fixed bed type or manufacturing type milling machines. 3. Planer type milling machines. 4. Production milling machines. 5. Special purpose machines. Further detailed classification and descriptions of these machines will follow in the

forthcoming articles.

Column and knee type milling machines: These machines are all general purpose

machines and have a single spindle only. They derive their name ‘Column and knee’

type from the fact that the work table is supported on a knee like casting, which can

slide in vertical direction along a vertical column. These machines, depending upon

the spindle position and table movements, are further classified as follows:

a) Hand‐milling machine, b) Plain or horizontal milling machine, c) Vertical milling machine, d) Universal milling machine, and e) Omniversal milling machine.



NAGPUR

6

Q ‐7 Dra

parts of

Vertical

This ma

type. Pr

1 and 2

made i

head, c

always

can be s

The kne

along t

saddle i

INSTITUTE

w a neat s

it.

milling m

chine is av

inciples pa

. It carries

tegral wit

n be of fi

emains ve

wivelled to

Fig

e carries a

e parallel

mounted

OF TECHNO

ketch of c

chine: It d

ilable in b

ts of the l

a vertical

the colu

ed type (

rtical and

any desire

.32 Vertica

n enclosed

vertical gu

on the kne

Fig 4.33 V

OGY

Question

lumn and

erives its

oth types;

tter type

column on

n and ca

ig 1) or s

an be adj

d angle to

l milling m

screw jac

ide‐ways

e and can

rtical milli

ank with s

knee type

ame from

the fixed b

re illustrat

a heavy b

rries housi

iveling ty

sted up a

machine t

chine wit

, by mean

rovided o

e moved,

g machin

olution

milling m

the vertic

ed types a

ed by mea

ase. The o

ng at its

e (Fig. 2)

d down. I

e inclined

fixed hea

s of which

the fron

long the

with swiv

Manufacturi

chine? An

al position

well as c

s of block

ver‐arm in

ront. This

In fixed ty

swiveling

urfaces.

it is move

side of t

lling head.

g process‐I

d explain

of the spi

lumn and

diagrams i

this machi

housing, c

pe, the sp

type, the

d up and

e column,

3rd

semest

ain

ndle.

knee

n Fig

ne is

alled

indle

head

own

The





3rd

semeste

87

Q ‐8 Explain milling machine power feed mechanism?

Milling machine mechanism: The milling machine mechanism is composed of spindle

drive mechanism and the table feed mechanism.

The spindle drive mechanism is incorporated in the column. All modern machines are

driven by individuals motors housed within the column, and the spindle receivers’

power from a combination of gears and clutch assembly, Multiple speed of spindle may

be obtained by altering the gear ratio.

Fig. 1. illustrated the power feed mechanism contained within the knee A of the

machine to enable the table C to have three different feed movements, i.e. longitudinal, cross, and vertical. The power is transmitted from the feed gear box H consisting of

change gears to shaft 23 in the knee A of the machine by a telescopic shaft 11. Both

ends of the shaft 11 are provided with universal joint 10 and 12. Telescopic shaft and

universal joints are necessary to allow vertical movement of knee A, gear 14, attached

to the jaw clutch 20, is keyed to the shaft 23 and drives gear 13 which free rotate on

shaft 23 and is in mesh with gear 19 fastened to the evaluating screw 15, 16 serves as a

nut for 15, and as screw in nut 17. 15 and 16 therefore serves as telescopic screw

combination and a vertical movement of the knee is thus possible. As soon as the clutch

20 is engaged with the clutch attached to the bevel gear 22 y means of a lever 4, 22

rotates and this being in mesh with gear 19 causes the elevating screw 15 to rotate in 16

giving a vertical movement of the knee. Like‐wise, when the clutch 21, which is keyed to

the cross feed screw 7 through gears 14 and 13. This causes the screw 7 to rotate in nut

6 of the clamp bed giving a crossfeed movement of the clamp bed D and saddle B.

Gear 18 is fastened to shaft 23, and meshes with gear 25 which is fastened to the

bevel gear 24. Again 24 meshes with gear 5 attached to a vertical shaft which carries at

its upper end another bevel gear 3. Gear meshes with gear 2 which is fastened to the

table feed screw1. Therefore, longitudinal feed movement of the table is possible

through gears 18, 25, 24, 5, 3, and 2.



NAGPUR

8

1

6

s

INSTITUTE

A Kn

. Longitudi

. Nut, 7. C

niversal j

rew, 23. F

OF TECHNO

Fig. 4.34 M

ee, B. Sad

F. Bed,

nal fed scr

ross‐feed s

int, 11. T

eed shaft.

OGY

Question

illing mach

le, C. Tabl

. Column,

w, 2, 3, 5,

crew, 8, 2

lescopic f

ank with s

ine power

, D. Clamp

. Feed ge

19,22,24.

, 21. Pow

ed shaft,

olution

feed mech

bed, E. Fe

r box.

evel gears,

r‐feed clu

13, 14, 1

Manufacturi

anism

d hand‐w

4. Clutch

tch, 9. Sad

, 25. Gea

g process‐I

eel,

perating l

dle nut, 10

s, 15 Elev

3rd

semest

ver,

, 12.

ting





3rd

semeste

89

GRINDING PROCESS AND SUFERFINISHING





3rd

semeste

91

beveled edge. The common shape of wheel faces is shown in Fig 5.2. The proper

selection of a particular type of face will depend on the nature of work.

Fig.5.2. Common shapes of grinding wheel faces.

BUILT‐UP

WHEELS:

‐

These wheels are made in many ways. Essentially, they consist of a number of

bonded abrasive blocks, held together by suitable means. A typical example of these will

consist of a these blocks fastened to a metal wheel, which consist of formed abrasive

blocks held in a circle by a chuck. Spacers are always provided between the blocks. It is

mainly employed on vertical spindle grinders with reciprocating or rotary type tables.

They are mainly used in surface grinding and carry the following main advantages:

It is easier to manufacture these wheels in large sizes in comparison to the solid wheels of same size. Fig. (5.3 segmental grinding

wheel)

They cut intermittently, and hence cool grinding is the result.

A segmental grinding wheel is shown in Fig. 5.3.

Other than those shown in Fig.5.1, there is a special variety of grinding wheels

which possesses ‘Cone’ and ‘Plug’ shapes. They are employed to grind intricate

shapes to which their outer surfaces suit. They carry threaded bushings on the

mounting side, as shown at (d) in Fig.5.4. This figure shows the standard Shapes

of ‘cone and plug’ grinders as per IS: 2324 (Part I)‐1985. Their detailed





3rd

semeste

92

dimensions are also given in this standard. An imported point to note is that in

this type of wheels grinding is performed by all the surfaces except the flat

surface on the mounting side.

Fig. 5.4 cone and plug grinding wheel as per IS: 2324 (PART‐ I)‐ 1985

Cone(type 16), (b) Cone (type 17), (c) Cone (type 17R), (d) plug(type 18), (e) Plug

(type18R), (f) Conical plug –square tip (type 19), (g) Conical plug –round tip (type 19R)

MOUNTED WHEELS AND POINTS:‐

These are small grinding wheels with shanks attached to them. They are

made in various different shapes and sizes so as to enable grinding even in those places

which are not easily accessible otherwise. (see Fig 5.5).





3rd

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93

Fig 5.5. Common shapes of mounted wheels and points

They are commonly used on portable grinders and run at extremely high speeds up to

100,000 r.p.m. A few of the applications of these wheels and points are in finishing dies,

metal moulds, recesses, small circular and tapered holes, fillets and other small

curvatures. Such requirements frequently occur in foundry, forging and tool room work,

such as for cleaning the surfaces of casting and forgings and production and

maintenance of tools and dies for die‐casting, plastic moldings, pressing (hot), drop

stamping and metal extrusion, etc.

DIAMOND WHEELS

These wheels are also made in almost similar shapes as of aluminium oxide or

silicon carbide wheels. They are also provided with the central hole for being mounted

on a spindle. Alternatively, they can be attached or fastened to metallic backing.

Artificial diamond bonded wheels are now preferred over the natural diamond bonded

wheels, particularly in grinding carbide tipped tools. The wheels may have a vitreous or

resinoid bond. It is reckoned that the artificial diamond bonded wheels are more free

cutting and enable more stock removal with less power consumption as compared to

the natural diamond bonded wheels.

METHOD OF SPECIFYING A GRINDING WHEEL

The methods of specifying a grinding wheel differ slightly in different

countries. In order to maintain uniformity throughout the country in the system of

marking grinding wheels the Bureau of Indian Standards has devised a standard system

to be followed by all manufactures. Its details are given in (IS: 551‐1954). According to

this system the various elements and characteristics of grinding wheels are represented

on all the wheels in definite sequences as follows:

1. Abrasive 2. Grain size or gril,

2. Grade 4. Structure and 5. Bond.

In addition, a manufacturer can use a suitable ‘prefix’, presiding the abrasive notation,

to indicate his own trade brand of the abrasive used and a ‘suffix’ at the end of all the

notations to indicate the manufacturer’s own symbolic representation for that

particular type of wheel. The use of prefix and /or suffix is, however, optional. The





3rd

semeste

94

marking system recommended by the Bureau of Indian Standards in there IS code No.

551‐1989 is given in Fig.(5.6).

Apart from the above information, in order to specify a grinding wheel completely, the

size, i.e., diameter and width or thickness and the diameter of bore are also required to

be mentioned.

Thus, a grinding wheel carrying the markings, 250 x 25 x 32 W A 46 L 4 V 17 will

confirm to the following specifications:

Wheel dia. = 250mm

Thickness of wheel = 25mm

Bore dia. = 32m

W‐‐‐‐Manufacturer’s prefix to abrasive. It is optional. Here it denotes ‘White’

A‐‐‐‐‐Abrasive (AL₂O₃)

46‐‐‐‐It is a grain size (medium)

L‐‐‐‐‐It is a grain medium grade.

4‐‐‐‐Represents a dense structure

V‐‐‐‐Stands for vitrified bond.

17‐‐‐‐It is a suffix denoting the ‘bond type’ of the manufacturer.

QUE‐2) DRAW A NET SKETCH TO GRINDING MACHINE, HORIZONTAL SPINDLE

RECIPROCATING TABLE TYPE SURFACE AND EXPLAIN FUNCTIONS OF ITS VARIOUS

PARTS?

RECIPROCATING TABLE TYPE SURFACE GRINDERS

The principal of grinding, as applied to reciprocating table type surface grinders, is

illustrated by means of the diagram of relative movements in Fig. 5.6 and 5.7 A

reciprocating table type surface grinder Wheel (see Fig. 5.6 or a vertical Spindle of the

same, as shown in Fig 5.6 The former will carry a straight wheel and the latter a cup type

wheel. Hydraulic drives are commonly used in all such grinders. Cutting is done on the





3rd

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95

periphery of the straight wheel in case horizontal spindle type, and on revolving edge of

the cup wheel on vertical spindle machines.

Fig.5.6 working principle of a horizontal spindle reciprocating table surface grinder.

The horizontal spindle machines are widely used in tool rooms. The work piece is usually

held on a magnetic chuck on these machines. They are vastly used for grinding flat

Surfaces. The machine size is designed by the dimensions of the working area of the

table. A typical design of a Grinder is shown in Fig.5.7 illustrating its main Parts and

controls. The longitudinal feed to the work is given by reciprocating the table. For giving

cross feed, there are two methods. One is to mount the table on a saddle and give the

cross feed by moving the saddle. Alternatively, the cross feed can be given by moving

the wheel‐head in and out. It is this method which is employed in the machine shown in

Fig. 5.7 In feed is provided by lowering the wheel‐head along the column.

In case of vertical spindle reciprocating table grinders the table, along with the work

piece, reciprocates under the wheel. The wheel covers all or a major portion

Fig. 5.7 Working principle of a vertical spindle reciprocating table surface grinder





3rd

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97

usual by moving the saddle. A manual or power feed can be employed to feed the

wheel‐head vertically. An individual motor drive is usually provided to rotate the wheel.

QUE‐3) WHAT DO YOU UNDERSTAND FROM ‘GRAIN’,’GRIT’ STRUCTURE AND GRADE

OF GRINDING WHEEL EXPLAIN?

GRAIN OR GRIT

The term ‘Grain’ or ‘Grit’ denotes the approximate size of the abrasive particles and give

an idea of the coarseness or fineness of the grinding wheel. A grinding wheel may have

the abrasive particles of same size or different sizes. The former is known as a straight

wheel and the latter compound wheel. The choice of grain‐size or grit depends upon

many factors, viz,, quality of finish required, amount of stock material to be removed

and physical properties of the material to be ground. The coarser grit will remove the

stock at a faster rate and finer finish will always require a finer grit. Coarse grit wheels

are more suitable for grinding soft and ductile materials hard and brittle materials are

best ground with finer grit wheels.

The grit or grain size of an abrasive is denoted by a number representing the

number of meshes per inch of the screen through which the grains of crushed abrasive

are passed for grating. The standard numbers representing different grain sizes are

given in Table.





3rd

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98

Grit

designation

Grain size or Grit No.

Coarse

Medium Fine

Very fine

10 12 14 16 20 24

30 36 46 54 60 80 100 120 150 180

220 240 280 320 400 500 600

Standard grain size for grinding wheels

Note. The first three types i.e. coarse, medium and fine, are used in grinding work and

the ‘very fine’ grit, i.e., having grain size no. from 220 onwards, in honing work.

GRADE:‐

The term ‘Grade’ indicates the strength of bond in a wheel, i.e., the power of the abrasive particles to hold together and resist disintegration under the cutting pressure.

Higher the proportion of bond for a specified quantity of abrasive particles the harder

will be the wheel and a lower proportion will render it ‘soft’. The abrasive grains of a

soft wheel will easily be broken away from the bond whereas the hard wheel will retain

these particles for a much longer period. The selection of a particle grade of wheel is

largely governed by the nature of work, its composition, size and hardness, etc. Softer

wheels are preferred for grinding harder materials and vice‐versa. Similarly, smaller the

size of the work, the harder should be the wheel and vice‐versa. The machine condition

also plays an important role in this selection. Where vibrations are likely to occur harder

wheels are employed, such as in tool post grinders on lathes. All wheels manufacturers

always provide tables of recommended grits and grills for specific operation and

materials to be machined and it is advisable to follow the same in selecting a wheel for a

specific job.

Different wheel grades are represented by English alphabets from A to Z, ‘A’

being the softest and ‘Z’ being the hardest. The standard grouping is as follows:

Soft

Medium

Hard

A B C D E F G H

I J K L M N O P

Q R S T U V W X Y Z

Different grades of grinding wheels





3rd

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99

STRUCTURE

This term denotes the spacing between the abrasive grains, or in other

words the density of the wheel. The proportion of the bond in a certain volume of the

wheel affects the structure. A higher proportion will render an open structure and a

lower proportion will lead to a closer structure. If two wheels of same grit and grade are

used on the same material, one having an open structure and the other close structure,

the former will be found to cut faster and more freely in comparison to the latter and

will have more life as compared to it.

The above two types of structures are represented by numbers as follows:

Structures of grinding wheels

Note. Selection of a particular structure will depend upon the hardness of work

material, Type of grinding operation and quality of surface finish needed on the work

surface. Brittle and hard materials and finish grinding work will need a dense structure,

while a soft and tough work material and rough grinding operation will need an open

structure.

QUE‐4) EXPLAINS DIFFERENT TYPES OF SURFSCE GRINDERS?

SURFACE GRINDERS:‐

Surface grinders do almost the same operation as the planers, shapers or milling

machines, but with more precision. Primarily they are intended to machine flat surface,

although irregular, curved or tapered surfaces can also be ground on them. The

common classification of surface grinders can be made as follows:

1. According to the table movement: (a) Reciprocating table type. (b) Rotary table type.

2. According to the direction of wheel spindles:

Structure type Represented by Nos.

Dense

Open

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 or

up





3rd

semeste

100

(a) Vertical spindle type. (b) Horizontal spindle type.

3. Special type and single purpose machines. (a) Face grinders (b) way grinders (c) Wet belt grinders.

RECIPROCATING TABLE TYPE SURFACE GRINDERS

The principal of grinding, as applied to reciprocating table type surface grinders, is

illustrated by means of the diagram of relative movements in Fig. 5.9 and 5.10 A

reciprocating table type surface grinder Wheel (see Fig. 5.9 or a vertical Spindle of the

same, as shown in Fig The former will carry a straight wheel and the latter a cup type

wheel. Hydraulic drives are commonly used in all such grinders. Cutting is done on the

periphery of the straight wheel in case horizontal spindle type, and on revolving edge of

the cup wheel on vertical spindle machines.

Fig.5.9 Working principle of a horizontal spindle reciprocating table surface grinder.

The horizontal spindle machines are widely used in tool rooms. The work piece is usually

held on a magnetic chuck on these machines. They are vastly used for grinding flat

Surfaces. The machine size is designed by the dimensions of the working area of the

table. A typical design of a Grinder is shown in Fig.5.10 illustrating its main Parts and

controls.

Fig. 5.10 Working principle of a vertical spindle reciprocating table surface grinder





3rd

semeste

101

The longitudinal feed to the work is given by reciprocating the table. For giving cross

feed, there are two methods. One is to mount the table on a saddle and give the cross

feed by moving the saddle. Alternatively, the cross feed can be given by moving the

wheel‐head in and out. It is this method which is employed in the machine shown in Fig. 5.10. In feed is provided by lowering the wheel‐head along the column.

In case of vertical spindle reciprocating table grinders the table, along with the

work piece, reciprocates under the wheel. The wheel covers all or a major portion

Fig. 5.11 Reciprocating table hydraulic surface grinder.

1. “Stop” push‐button for hydraulic pump motor, 2.”Start” push‐button for hydraulic pump motor, 3. Adjustable travel cum‐dog, 4. Master “Stop” push‐

button. 5. Push button for engaging rapid upward traverse of the wheel head. 6.

Control lever of Electromagnetic ebuck (“switched on”, “switched off” and

“demagnetized”).7. Signal lamp indicating that electromagnetic chuck is switched

on. 8. Electromagnetic chuck operation switch (“with chuck” or “without chuck”).

9. Feed switch on and off. 10. “Start” push‐button for coolant pump motor. 11.

Work light switch. 12. Push button for engaging rapid downward traverse of the

wheel head. 13. Change‐over switch for starting coolant flow either together with

grinding wheel rotating or together with table travel. 14. “Stop” push‐button for

grinding wheel rotation. 15. “Start” push‐button for grinding wheel rotation. 16.

Lever for table travel. (“start”, “stop”).17. Lever for manually reversing table

travel. 18. Knob for setting table speed. 19. Push‐ button for disengaging band

wheel and dial.20. Handwheel for vertical wheel head feed. 21. Lever for setting



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NAGPUR

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3rd

semeste

105

Fig 5.14 Simplified dia. of a centre less grinder.

The relative movements of the work piece and the two wheels are shown in fig.5.14.

The principle of centre less grinding is used for both the external grinding as well as

internal grinding. Many hollow cylindrical and tapered work pieces, like bushes, pistons,

valves tubes and balls, etc, which either do not or cannot have centre, are best ground

on centre less grinders.

A simplified diagram of centre less grinder is shown in Fig. 5.14 illustrating its main

parts and controls. It carries a heavy base and two wheel heads, one carrying the

grinding wheel (large one) and the other regulating wheel(smaller one3). The work

piece rests on the blade of the work rest between these two wheels. Each head carries a

separate wheel truing mechanism for the wheel it carries. A housing can provide on one side of the machine body to house the main driving motor. There are two control panels

on the front. The left hand panel carries control of speed adjustment of the two truing

mechanism and the in‐feed grinding mechanism. The right hand panel carries for

hydraulic mechanism, speed adjustment of regulating wheel, automatic working cycle

switch, start and stop switches, etc.

In operation, grinding operation is performed by the grinding wheel only while

the function of the regulating wheel is to provide the required support to the work

pieces while it is pushed away by the cutting pressure of the grinding wheel. This helps the work pieces to remain in contact with the grinding wheel. At the same time,

required support from bottom is provided by the work rest as the work piece, while

rotating, and rests on the blade of the work rest. The regulating wheel essentially carries

rubber bond and helps in the rotation of work piece due to friction. The direction of

rotation of the two wheels is the same. The common methods used for feeding the

work are:

1. Through feed 2. In‐feed 3. End feed

1. Through feed grinding: In this method of centre less grinding, the work piece is

supported and revolved as described above but, is simultaneously given an axial

movement also by the regulating wheel and guides so as to pass between the

wheels.



1

NAGPUR

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3rd

semeste

108

6. Since there is no end thrust, there are no chances of any springy action or distortion in long work pieces.

7. The operation condition automatically provides a true floating type centre for the work pieces and, as such, the common errors normally associated with the centre and centre holes are automatically eliminated.

8. The work piece is supported rigidly during the operation and can be subjected to heavy cuts, resulting in a rapid and more economical grinding.

9. Since the need for marking and making centre holes is totally eliminated and a smaller grinding allowance is needed, the grinding time is considerably

reduced.

10. Large grinding wheels are used and errors due to wheel wear are reduced. So, the requirement of wheel adjustment is minimum.

11. A heavy little maintenance is needed for the machine. 12. Very highly skilled operations are not needed for operating centre less

grinders.

13. Direct adjustment for sizes can be made, resulting in a higher accuracy. 14. A fairly wide range of components can be ground.

Some disadvantages are:‐

1) In hollow work there is no certainly that the outside diameter will be concentric

with the inside diameter.

2) Work having multiple diameters is not easily handled.

QUE‐6) EXPLAINS THE PROCESS OF HONING AND LAPPING?

LAPPING

It is an abrading process employed for improving the surface finish by

reducing roughness, waviness and other irregularities on the surface. It is used on both

heat‐treated and non heat‐treated metal parts. It should however, be noted that where

good appearance of the job surface is the only requirement, it should not be employed,

since there are other finishing methods which will give the same desired result with low





3rd

semeste

109

cost. It should be used only where accuracy is a vital consideration in addition to the

surface finish. The basic purpose of lapping is to minimize the extremely minute

irregularities left on the job surface after some machining operation.

In brief, we can say that Lapping is basically employed for removing minor

surface imperfection, obtaining geometrically true surfaces, obtaining better

dimensional accuracy and, thus, facilitate a very close fit between two contacting

surfaces.

The material to be selected for making a lapping tool or lap largely depends

upon the individual choice and the availability, and no specific rule can be laid for the

same. The only consideration that has to be made is that the material used for making a

lap should be soft so that the abrasive grain can be easily embedded in its surface. In case a hard material is used for making the lap, the abrasive particles will quickly go out

of their places. The commonly used material is soft cast iron, copper, brass, lead and

sometimes hardwood.

Abrasive: All the abrasive, i.e., natural as well as artificial are used for lapping.

Aluminium oxide is preferred for lapping soft ferrous and non‐ferrous metals. Silicon

carbide and natural corundum are used for hardened steel parts. Powdered garnet is

used for lapping soft ferrous and non‐ferrous metals, emery for hardened steel

components and diamond for extremely hard material like cemented carbides.

Vehicle:

The term ‘vehicle’ in lapping denotes the lubricant used to hold or retain the abrasive

grains during the operation. To some extent it also controls the cutting action of the

latter. Some common vehicle used in lapping includes the vegetable or olive oil, hard oil,

water so9luble oil, mineral oil, kerosene mixed with a little machine oil, alcohol, and

heavy grease. For cleaning the laps, naphtha is commonly used. No specific

recommendation can, although, be laid for the selection of a particular vehicle, still the

vehicle used should posses the following qualities:

1. It should be able to hold the abrasive particles uniformly during the operation. 2. Its viscosity should not be considerably affected by temperature changes. 3. It should not evaporate quickly.



1

NAGPUR

10

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Lapping

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2. By m

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3rd

semeste

111

Fig. 5.18 An example of Hand Lapping

Machine lapping:

Machine lapping is performed for obtaining a highly finished surface on many articles

like races ball and roller bearings, gears, crankshafts, machine bearings, pistons, pins

and gauges, gauge blocks, various automobile engine parts and micrometer spindles,

etc.

Fig 5. 19 working principle of a vertical spindle lapping machine.

HONING

It is also an abrading process, used for finishing previously machined surfaces. It

is mostly used for finishing internal cylindrical surfaces such as drilled or bored holes.

The tool used, called a hone, is a bonded abrasive hone made in the form of a stick.

Although honing cradles the maximum stock removal out of the surface finishing

operation, still it is not primarily a metal removing operation. However, this higher stock

removing capacity enables the application of honing for correcting slight out of

roundness or lapper. Hole location cannot be corrected through it. The usual amount of

stock left for removal by honing is form 0.1 mm to 0.25 mm; although it is capable of

removing the stock up to 0.75 mm. Honing is performed at relatively slow speeds in the

range of 10‐30 m/min.

The honing stock are so held in a holder or mandrel that they can be forced outwards

by mechanical or hydraulic pressure against the surface of the bore. Aluminium oxide,



1

NAGPUR

12

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1

NAGPUR

13

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1

NAGPUR

14

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1

NAGPUR

16

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3rd

semeste

119

disturbed. It is the tailstock centre which is moved in or out, manually or

hydraulically, to insert and hold the work. Tailstock and headstock both can be

moved along the table to suit the work. The table is usually made in two parts. The

upper table carries the tailstock, headstock and the work piece and can be swiveled in a horizontal plane to a maximum guideways to provide longitudinal traverse to the

upper table, and hence the work. Table is usually preferred.

Universal cylindrical grinders.:‐

A universal cylindrical grinder carries all the parts and movement of a plain

cylindrical grinder and, in addition, carries the following advantageous

features.

a) Its headstock, can be made to carry a live or dead spindle, as desired the former being needed when the work is held in a chuck.

b) The headstock can itself be swiveled in a horizontal plane. c) Its wheel head can be raised or lower and can also be swiveled to +_ 900 to grind

tapered surface having large taper angle.

All these factors contribute towards the greater versatility of these grinders. All the

modern universal type cylindrical grinders carry hydraulic drive for wheel head

approach and feed, table traverse and elimination of backlash in the feed screw nut.

A typical hydraulically operated universal cylindrically grinders, with its main parts

control.

Most of the modern universal grinders are provided with necessary extra equipment

like work rest to support slender work, wheel trueing device, arbour for balancing

the wheel, internal grinding spindle and three jaw self ‐centering chuck, etc.





3rd

semeste

120

DRILLING MACHINE, BORING, BROACHING AND REAMING MACHINES





3rd

semeste

121

UNIT‐VI

DRILLING MACHINE,

BORING,

BROACHING

AND

REAMING

MACHINES

Q ‐1 Describe the different operations which are performed on drilling machine with

neat sketches.

There is no. of operations done on a drilling machine, as shown in Fig 6.1. these are as

follows:

1. Drilling 5. Counter‐ sinking 2. Reaming 6. Spot facing, and

3. Boring 7. Tapping

4. Counter‐ boring 1. Drilling:‐

It is the main operation done on this machine. It is the operation of producing the

circular hole in a solid metal by means of a revolving tool called drill.

2. Reaming:

‐

It is the operation of finishing a hole to bring it to accurate size and have a fine surface

finish. The operation is performed by means of a multi‐tooth tool called reamer. The

operation serves to produce a straight, smooth and accurate hole. The accuracy to be

expected is within ± 0.005 mm.





3rd

semeste

122

Fig.6.1. Operations done on drilling machine

3. Boring:‐

It is an operation used for enlarging a hole to bring it to the required size and have a

better finish. It involves the used of an adjustable cutting tool having a single cutting

edge. In addition to the above objective, this operation can be used for correcting the

hole location and out of roundness, if any, as the tool can be adjusted to remove more metal from one side of the hole than the other. It is a slower process than reaming. The

accuracy to be expected is within ± 0.0125 mm.

4. Counter‐ boring:‐

The operation is used for enlarging only a limited the portion of the hole is called

counter‐ boring. It can be performed either by a means of a double‐tool boring bar, or a

counter‐ boring tool. In order to maintain alignment and true concentricity of the

counter bored hole with the previously drilled hole the counter‐ boring tool is provided with a pilot at its bottom.

5. Counter‐ sinking:‐

It is the operation used for enlarging the end of a hole to give it’s a conical shape for a

short distance. This is done for providing a seat for the counter‐ sunk heads of the





3rd

semeste

123

screw, show that the letter may be flush with the main surface of the work. The

standard counter‐ sinks carry included angles of 600, 82

0 or 90

0.

6. Spot facing:‐

This operation is used for squaring and finishing the surface around and at the end of

hole, so that the same can be provide smooth and true seat to the underside of bolt

heads or collars, etc. This is usually done on casting or forgings. The whole may be spot

faced below the rough surface or above it. i.e., on the upper surface of the boss, if the

same is provided.

7. Tapping:‐

It is the operation done for forming the internal threads by means of the tool called tap. To perform this operation the machine should be equipped with a reversible motor or

some other reversing mechanism. Alternatively, a collapsible tight typing attachment is

used.

Q ‐2 Explain with neat sketch planer type horizontal boring machine.

This machine resembles in construction with the table type only the difference is in the

construction and operation of the work supporting mechanism. In this, a heavy cross

bed is incorporated between the spindle column and the end support column. This is

mounted across the axis of the spindle and carries a table over it. On its two sides it

carries the two columns. The main column carrying the head‐stock, rigidly fixed

whereas the end‐support column can move towards or away from this bed along the

horizontal ways provided on the top of the cross bed, at right angles to the former bed.

The job is mounted on the table. In operation it resembles a planer





3rd

semeste

124

Fig. 6.2. Block diagram of a planer type boring machine.

1. End support column. 2. Spindle head column. 3. Table. 4. Spindle. 5. Spindle head. 6. Cross bed. 7. Electric motor for spindle head. 8. Longitudinal bed.

In that tool is held between the two columns or mounted on the headstock only and the

work, mounted on the table, moves past the tool. (See Fig 6.2). This type of machine is

very suitable for long jobs.

Q ‐3 Draw neat sketch of a twist drill and show its various elements clearly?

The most common type of drill in use today is the twist drill. It was originally

manufactured by twisting a flat piece of tool steel longitudinally for several revolutions,

then grinding the diameter and the point. The present day twist drills made by

machining two spiral flutes or grooves that turn lengthwise around the body of the drill.

Fig. 6.3. Principle parts of twist drills





3rd

semeste

125

Twist drill is an end cutting tool. Different types of twist drills are classified by Indian

Standard Institution according to the type of shank, length of the flute and overall

length of the drill.

Twist drill elements:

The following are the twist drill elements.

Axis: The longitudinal centre line of the drill.

Body: That portion of the drill extending from its extreme point to the commencement

of the neck, if present, otherwise extending to the commencement of the shank.

Body clearance: The portion of the body surface which is reduced in diameter to

provide diametric clearance.

Chisel edge: The edge formed by the intersection of the flanks. The chisel edge is also

sometimes called dead centre. The dead centre or the chisel angle acts as a flat drill and

cuts its own hole in the work‐piece. A great amount of axial thrust is required to cut a

hole by the chisel edge. In some drills chisel edge is made spiral instead of a straight

one. This reduces the axial thrust and improves the whole location. Chances of

production of oversize holes are also reduced.

Chisel edge

corner:

‐

The corner formed by the intersection of a lip and the chisel edge.

Face:‐

The portion of the flute surface adjacent to the lip on which the chip impinges as it is cut

from the work.

Flank;‐

That surface on a drill point which extends behind the lip to the following flute.

Flutes:‐

It is the groove in the body of the drill which provides the lip.

The functions of flutes are:‐





3rd

semeste

126

1. To form the cutting edges on the point.

2. To allow the chips to escape.

3. To cause the chips to curl. 4. To permit the cutting fluid to reach the cutting edges.

Heel: ‐ the edge formed by the intersection of the flute surface and the body clearance.

Lands:‐

The cylindrically ground surface on the leading edges of the drill flutes. The width of the

land is measured at the right angles to the flute helix. The drill is full size only across the

lands at the point end. Land keeps the drill aligned.

Lip (cutting edge):‐

The edge formed by the intersections of the flank and the face. The requirements of the

drill lips are:‐

1. Both lips should be at the same angle of inclination with the drill axis, 590 for general work.

2. Both lips should be of the equal length. 3. Both lips should be provided with the correct clearance.

Neck:‐

It is the diametrically undercut portion between the body and shank of drill. Diameter

and other particulars of the drill are engraved at the neck.

Outer corner:‐

The corner formed by the intersection of the flank and face.

Point:‐

The sharpened end of the drill, consisting of all that part of the drill which is shape to

produce lips, face, flanks and chisel edge.

Right hand cutting drill:‐





3rd

semeste

127

A drill which cuts when rotating in counter ‐ clockwise direction viewed on the point end

of the drill.

Shank:‐

That part of the drill by which it is held and driven. The most common types of the shank

are the taper shank and the straight shank. The taper shank provides the means of

centering and holding the drill by friction in the tapered end of the spindle.

Tang:‐

The flattened end of the tapered shank intended to fit into a drift slot in the spindle,

socket or drill holder. The tang ensures positive drive of the drill from the drill spindle.

Web:‐

The central portion of the drill situated between the roots of the flutes and extending

from the point towards the shank; the point end of the web or core forms the chisel

edge.

Linear dimensions:

‐

The following are the linear dimensions of the drill:

Back taper (longitudinal clearance):‐

It is the reduction in diameter of the drill from the point toward the shank. This permits

all parts of the drill behind the point to clear and not rub against the sides of the hole

being the drilled the paper varies from 1:4000 for small diameter drills to 1: 700 for

larger diameters.

Body clearance diameter:‐

It is the diameter over the surface of the drill body which is situated behind the lands.

Depth of the body clearance:‐

The amount of radial reduction on each side to provide body clearance.





3rd

semeste

128

Diameter:‐

The measurements across the cylindrical lands at the outer corners of the drill.

Flute length:

‐

The axial length from the extreme end of the point to the termination of the flute at the

shank end of the body.

Lead of helix:

The distance measured parallel to the drill axis between the corresponding point on the

leading edge of the flute in one complete turn of the flute.

Lip length:

‐

The minimum distance between the outer corner and the chisel end corner of the lip.

Overall length:‐

The length over the extreme ends of the points and the shank of the drill.

Web (Core) taper:‐

The increase in the web or core thickness from the point of the drill into the shank end

of the flute this increase in thickness gives additional rigidity to the drill and reduces the

cutting pressure at the point end.

Web thickness:‐

The minimum dimensions of the web or core measured at the point end of drill.

Considerable power is required to force portion the work, and web thinning is employed

to reduce the web thickness.

Drill angles:‐ Following are the drill angles which are ground on a twist drill for efficient

removal of metal.

Chisel edge angle: The obtuse angle included between the chisel edge and the lip as

viewed from the end of the drill. The usual value of this angle varies from 1200 to 135

0.





3rd

semeste

129

Helix angle or rake angle: The helix or rake angle is the angle formed by the leading edge

of the land with a plane having the axis of the drill. If the flute is straight, parallel to the

drill axis then there would be no rake; if the flute is right handed then it is positive rake;

and if it is left handed then the rake is negative. The usual value of rake angle is 300

, angle, greater will be torque required to drive the drill at a given feed.

Point angle: This is the angle included between the two lips projected upon a plane,

parallel to the drill axis and parallel to the two cutting lips. The usual point angle is 1180,

but for harder steel alloys, the angle increases.

Lip clearance angle: The angle formed by the flank and a plane at right angles to the drill

axis. The angle is normally measured at the periphery of the drill. Lip clearance is the

relief that is ground to the edges in order to allow the drill to enter the metal without interference. The lip clearance angle should increase toward the centre of the drill than

at the circumference. This is due to the fact that different cutting edges follow different

helical paths. Any point on the cutting edge near centre. This happens to be such due to

the lead of the helix being same in each case and hence the clearance angle given to the

drill cutting edge should increase towards the centre/. The clearance angle is 120 in most

cases. The clearance angle should be minimum to add rigidity and strength to the

cutting edge.

Q ‐4 Draw a neat sketch of radial drilling machine, Name the various parts and their

functions.

The radial drilling machine is intended for drilling medium to large and heavy work‐

pieces. The machine consists of a heavy, round, vertical column mounted on a large

base. The column supports a radial arm which can be raised and lowered to

accommodate work‐pieces of different heights. The arm may be swung around to any

position over the work bed. The drill head containing mechanism for rotating and

feeding the drill is mounted on a radial arm and can be moved horizontally on the guide‐

ways and clamped at any desired position. These three movements in a radial drilling

machine when combined together permit the drill to be located at any desired point on

a large work‐piece for drilling the hole. When several holes are drilled on a large work‐

piece, the position of the arm and the drill head is altered so that the drill spindle may

be moved from one position to the other after drilling the hole without altering the





3rd

semeste

130

setting of the work. This versatility of the machine allows it to work is very large it may

be placed on the floor or in a pit. Fig 6.4 illustrates a radial drilling machine.

Figure 6.4 Radial drilling machine.

1. Base, 2. Column, 3. Radial arm, 4. Motor for elevating the arm, 5. Elevating screw, 6. Guide ways, 7. Motor for driving the drill spindle, 8. Drill head, 9. Drill spindle,

10. Table.

Plain radial drilling machine: In a plain radial drilling machine provisions are made for

vertical adjustment of the arm, horizontal movement of the drill head along the arm,

and circular movement of the arm in horizontal plane about the vertical column.

Semi‐universal machine: In a semi‐universal machine, in addition to the above three

movements, the drill head can be swung about a horizontal axis perpendicular to the

arm. This fourth movement of the drill head permits drilling hole at an angle to the

horizontal plane other than the normal position.





3rd

semeste

131

Universal machine: In a universal machine, in addition to the above four movements,

the arm holding the drill head may be rotated on a horizontal axis. All these five

movements in a universal machine enable it to drill on a work‐piece at any angle.

Q ‐5 Explains jig boring operation.

Jig boring machine is the most accurate of all machine tools. This was first developed in

the year 1910 in Switzerland and used as a locating machine. The real jig borer was first

built in the year 1917 by Pratt and Whitney. They are characterized by provisions of

highest accuracy through rigidity, low thermal expansion and precise means of

measuring distance for accurately locating and spacing holes. The machining accuracy is

very high, within a range of 0.0025 mm. A jig boring machine resembles in appearance

to vertical milling machine, but so far its operation and accuracy are concerned there

cannot be any comparison between the two. The spindle and other parts of the machine

are extremely rigid to resist deflection and the vibration is minimum. The spindle runs in

preloaded anti‐friction bearings. The spindle housings are made of invar having a very

low coefficient of linear expansion. The jig boring machine requires to be operated in

temperature controlled rooms where temperature can be maintained constant. This is

essential to prevent inaccuracy in the machine.

Types of Jig boring machines: There are mainly two types of jig boring machines:

1. Vertical milling machine type. 2. Planer type 1. Vertical milling machine type: It resembles in construction to a vertical milling

machine. The spindle rotates on a vertical column and the horizontal table rests

on the bed in front of the column. The positioning of the work mounted on the

table may be obtained by compound movements of the table, perpendicular and

parallel to the column face.

2. Planer type: It consists of two vertical columns at the two sides of the table and a mounted on the base. The table has reciprocating movement for adjustment of

the work. The spindle is mounted on the cross‐rail bridging the two vertical

columns. Ina planer type jig borer, two co‐ordinate movements for hole location

are provided by the longitudinal movement of the spindle along the cross‐rail.



1

NAGPUR

32

Q ‐6 Wh

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ad: The an

in to hole.

at portion

cement o

land: The

edge of th

e:

OF TECHNO

g? Draw

ractically

this, i.e.,

rilled a littl

ine. The o

r:

amer are d

al centre l

reduction

ds the sha

gular cutti

It is not pro

F

of the rea

its shank.

cylindrical

land.

OGY

Question

sketch of

ossible to

to produc

e undersiz

eration of

escribed a

ine of the

in a diam

k.

g portion

vide with

ig 6.5 mac

mer exten

ly ground

ank with s

reamer.

roduce a

an exactl

and then

reaming i

below:

eamer.

eter per

t the ente

circular la

ine reame

ing from t

surface a

olution

ole of the

y round a

reamed.

volves the

00 mm le

ring end t

nd.

he enterin

jacent to

Manufacturi

exact size

d smooth

eaming ca

multi‐toot

ngth of re

facilitate

end of th

the cuttin

g process‐I

hrough drihole of co

n be done

h tool call

amer from

he entry o

reamer t

edge, o

3rd

semest

lling.

rrect

both

d as

the

f the

the

the





3rd

semeste

133

1. Primary: That portion of the land removed to provide clearance immediately behind the cutting edge.

2. Secondary: That portion of the land removed to provide clearance behind the primary clearance or cutting edge.

Cutting edge: The edge formed by the intersection of the face and the circular land or

the surface left by the provision of primary clearance.

Face: The portion of the flute surface adjacent to the cutting edge on a which the chip

impinges as it is cut from the work.

Flutes: The grooves in the body of the reamer to provide cutting edges, to permit the

removal of chips and to allow cutting fluid to reach the cutting edges.

Heel: The edge formed by the intersection of the surface left by the provision of

secondary clearance and the flute.

Land: That portion of the fluted body left standing between the flutes, the surfaces

included between the cutting edge and the heel.

Pilot: A cylindrically ground portion of the body at the entering end of the reamer to

keep the reamer in alignment.

Recess: That portion of the body which is reduced in diameter below the cutting edge,

pilot or guided diameter.

Shank: That portion of the reamer by which it is held and driven.

Diameter: The maximum cutting diameter of the reamer at the entering end.

Rotation of cutting: A reamer is named, according to the direction of rotation as:

Left hand cutting reamer: A reamer which cuts while rotating in a clockwise direction,

when viewed on the entering end of the reamer.

Right hand cutting reamer: A reamer which cuts while rotating in a anti‐clockwise

direction, when viewed on the entering end of the reamer.





3rd

semeste

134

Reamer angles: The reamer angles are given below.

Bevel lead angle: The angle formed by the cutting edges of the bevel lead and the

reamer axis.

Clearance angles: The angles formed by the primary or secondary clearances and the

tangent to the periphery of the reamer at the cutting edge.

Helix angle: The angle between the cutting edge and the reamer axis.

Rake angle: The angles, in a diametric plane, formed by the face and a radial line from

the cutting edge.

1. If the face and the radial line coincide, the angle is zero degree and the face is called radial.

2. If the angle formed by the face and the radial line falls in behind the radial line in relation to the direction of cut, the rake angle is negative, and the face is known

as over‐cut.

Taper lead angle: The angle formed by the cutting edges of the taper lead and the

reamer axis.

Q ‐7 Differentiate with neat sketches between counter boring and countersinking

operations. Also sate their necessity.

Counter‐boring Counter‐sinking

• This operation is used for enlarging

only limited portion of the hole.

• This operation is used for enlarging

the end of the hole to give it a

emical shape for a short distance.

• The tool is used for counter‐boring

is called as counter‐bore.

• The tool is used for counter‐sinking

is called as counter‐sink.

• The enlarged hole forms a square • The enlarged hole form emical





3rd

semeste

135

shoulder with a original hole. shape with original hole.

• This is necessary in some cases to

accommodate the heads of bolts,

studs and pins.

• This is necessary in some cases to

provide a seat for the counter‐sunk

heads of the screws.

Fig 6.6 Counter‐boring Fig 6.7 Counter‐sinking

Q ‐8 Differentiate operations of drilling, boring and reaming clearly?

Drilling Boring Reaming

• The hole is generated by a

rotating edge of

cutting tool known

as the drill and

operation known as

the drilling.

• It is the operation of enlarging and

turning a hole

produced by

punching, casting or

forging.

• It is the operation of finishing and giving

dimensions accuracy

to hole or bore hole.

• The speed of spindle

is double than that

of boring and much

more than reaming.


is half than that of

drilling but more

than reaming.


is less than that of

drilling and boring.

• A 12 mm drill may

produce a hole as

much as 0.125 mm

oversize and 22 mm

drill may produce as

much as 0.5 mm

• The material

removed by this

process is around

0.375 mm and for

accurate work

should not be

• The accuracy is as

high as ± 0.00125

mm.



1

NAGPUR

37

A vertic

and cu

rolling s

circular

machin

The ver

(

(

1.

INSTITUTE

l boring m

bersome

tock tires,

shaped pa

can take

ical boring

) Vertical ) Standar

ertical tur

OF TECHNO

Fig

achine is p

ork‐piece

steam and

rts. The siz

nly circula

machine is

urret lathe

vertical b

et lathe:

OGY

Question

.6.8 Vertic

articularly

. The typic

water tur

e of the w

cut.

of two typ

, and

ring machi

ank with s

l boring m

dapted fo

al works a

ine castin

rk is limit

es:

ne

olution

chine

holding a

e: larger g

s, fly whe

d by the

Manufacturi

d machini

ar blanks,

els flanges

iameter o

g process‐I

ng large, h

locomotiv

and numb

the table.

3rd

semest

avy,

and

er of

The





3rd

semeste

138

fig 6.9 Vertical turret lathe

This type of boring machine combines the advantages of the vertical boring mill and the

turret the lathe. A vertical boring machine of smaller size is called a vertical turret lathe.

It has an indexible turret mounted upon the cross‐rail above the table for multiple

tooling. A four station square turret side‐head which enables facing‐turning under‐

cutting and many other operations is mounted at the side of the lathe. The cross‐rail

may have vertical adjustments and for case of operation it is counter balanced. The

turret mounted on the saddle may be moved cross‐wise by hand or power. The turret

may also be moved in a vertical plane. The side‐head also has up and down and to and

fro adjustments from the centre of the table. The machine is suitable for boring and

turning railroad wheels, piston rings, gear blanks, etc. A vertical turret lathe is shown in

Fig 6.9

2. Standard vertical boring machine: Vertical boring machines are larger in size than vertical turret lathe and there is no turret head. The machine is provided

with two vertical heads and one or two side‐heads. The tool‐heads are mounted

on the cross‐rail which may be adjusted up and down. The saddle of the tool‐

head may be fed cross‐wise and the tool head ram fed in vertical direction.





3rd

semeste

139

Fig. 6.10 Standard vertical boring machine

The ram heads can be swiveled to incline the ram up to 600 on either side of the vertical

axis for machining tapers. The machine is particularly intended for boring large,

cylindrical and symmetrical work‐pieces. Turbine castings, locomotive tires, etc. are

some of the common examples which need vertical boring machine is shown in Fig 6.10

b) Time estimation for drilling operations: Machining time in drilling is determined by the formula:

L

T = ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐min.

n x s r Where, n = r. p. m. of the drill

s r = Feed per revolution of the drill in mm

L = Length of travel of the drill in mm

And T = Machining time in min



1

NAGPUR

40

Where,

iii)

INSTITUTE

l1 = len

l2 = a

l3 = le

l4 = ov

A broac

Broachin

surfaces,

to enlar

punchin

OF TECHNO

F

th of the

proach of

gth of the

er‐travel

ing tool:

g of inside

external o

ge and c

, casting, f

OGY

Question

ig. 6.11 Dril

ork‐piece

drill,

drill point

Fi

surfaces c

r surface

t various

orging, etc.

Fig 6.13 B

ank with s

ling

6.12 broa

alled inter

roaching. I

contours

roach teet

olution

h terms

al or hole

nternal br

in holes

details

Manufacturi

broaching

aching to

lready m

g process‐I

and of ou

ls are desi

de by dri

3rd

semest

tside

ned

lling,





3rd

semeste

141

Broach elements: Ordinary cut broaches for machining previously drilled or

bored holes consist of the following elements (Fig. 6.9)

Pull end: This is designed to permit engagement of the broach with the

broaching machine through the use of a puller head.

Front pilot: This centers the broach in the hole before the teeth begin to cut.

Roughing and semi‐finish teeth: They remove most of the stock in the hole.

Finishing teeth: They are for sizing the hole and must have the shape required

of the finished hole.

Rear pilot and follower rest: They support the broach after the last tooth

leaves the hole.

The form of broach teeth reveals features like those of other cutting tools.

Land: The top portion of a tooth is called the land and in most cases ground to

give a slight clearance.

Back off or clearance angle: This corresponds to the rake angle on a lathe

tool. This is 1.50 to 2

0 for both cast iron and steel. Finish teeth have a smaller

angle ranging from 0 to 1.50.

Rake or hook angle or face angle: This corresponds to the rake angle on a

lathe tool. The rake angle varies from according to the material being cut, and

in general, increases as the ductility increases. Values of this angle for most

steels range from 12 to 150.

Pitch: The linear distance from the cutting edge of one tooth to the corresponding

edge on the next tooth is called the pitch t and differs for cutting and finishing teeth.

For the cutting teeth, the pitch is selected in accordance with the length l of the hole

being broached (t=1.25√ to1.5√ ). On an average, the pitch of finishing teeth is usually equal to one half of the cutting teeth pitch. The pitch should vary by 0.2 to

0.3 mm after several teeth.

The height of the roughing and semi finish teeth gradually increases from shank

to the finishing teeth. This increment, called the cut per tooth, depends on the

material being machined and the hole size. The cut per tooth is usually taken from

0.01 to 0.2 mm.





3rd

semeste

142





3rd

semeste

143

;





3rd

semeste

94905372 manufacturing process i

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