datta meghe college of engineering - basic...

DATTA MEGHE COLLEGE OF ENGINEERING, AIROLI

DEPARTMENT OF MECHANICAL ENGINEERING

DMCE AIROLI/MECHANICAL ENGINEERING/BASIC WORKSHOP PRACTICE-I MANUAL/AY 2018-19

BASIC WORKSHOP PRACTICE - I

(FEL101)

LABORATORY MANUAL

NAME OF THE STUDENT: ________________________________________________

YEAR / SEM / DIV / BATCH: _______________________________________________

ROLL NO: ______________________________________________________________




DATTA MEGHE COLLEGE OF ENGINEERING

AIROLI, NAVI MUMBAI


C E R T I F I C A T E

This is to certify that Mr. / Miss___________________________________________________

of Class First Year Division ___________ & Roll No. _____________________

Subject _____________________________________________has performed the experiments

mentioned in the index, on the date _____________________ in the premises of this institution.

Practical In charge: ___________________________________________

Head of Department: ___________________________________________

Principal: ___________________________________________

DATE: _________________

Examined on,

Examiner 1:_____________________ Examiner 2:_____________________




INDEX

Sr. No. Particular Page No.

01 List of experiments 04

02 Syllabus 05

03 Instructions for Laboratory 06

04 Carpentry Section 07

� Work Holding Devices/ Clamping Tools. 07

� Measuring Tools. 09

� Marking Tools. 10

� Cutting Tools. 12

� Striking Tools. 14

� Drilling Tools. 14

� Miscellaneous Tools. 15

� Wood Turning 17

� Wood Turning shapes 19

05 Welding Section 20

� Introduction 21

� Welding transformers 21

� Welding Electrodes 22

� Welding Tools 24

� Techniques of Welding 25




� Welding Joints 26

06 Machining Process 27

� Principal parts of lathe 27

� Work holding devices 30

� Measuring Instruments 30

� Lathe Operations 32

LIST OF EXPERIMENTS

SECTION EXP. NO NAME OF THE EXPERIMENTS

Signature

of

Instructor

CARPENTRY 1 Half Cross Lap Joint & Wood Turning

WELDING 2 Types of Welding Joints

MACHINING

PROCESS 3 Plain and Taper Turning




BASIC WORKSHOP PRACTICE – I (FEL101)

Syllabus (Common to all branches)

OBJECTIVES:

The objective is to impart training to help the students develop engineering skill sets. This

exercise also aims in inculcating respect for physical work and hard labor in addition to some

amount of value addition by getting exposed to interdisciplinary engineering domains.

OUTCOMES: Learner will be able to…

Basic practice sessions must be conducted in the trades mentioned and then products of

Industrial application (with combination of different trades) may be produced with the available

resources.

• Ascertain and select measuring instrument and measure dimension of components

and evaluate for accuracy.

• Make choices to carry out routine jobs of marking out the components for

planning, chiseling, wood & metal turning, filing, sawing, welding, fitting and

allied operations where choices are clear.

• Demonstrate practical skills by using appropriate tools & equipments.

• Explain and apply working principle of welding, perform ARC & gas welding

and wood & metal turning using appropriate materials with minimal assistance.

TRADE FOR EXERCISES:

• CARPENTRY SECTION

• Use and setting of hand tools like hacksaws, jack planes, chisels and gauges for construction

of various joints, wood tuning and modern wood turning methods.

• Term work to include one carpentry job involving a joint and report on demonstration of a

job involving wood turning.

TRADES FOR DEMONSTRATION AND HANDS ON EXPERIENCE:

• WELDING SECTION

• Edge preparation for welding jobs. Arc welding for different job like, Lap welding of two

plates, butt welding of plates with simple cover, arc welding to join plates at right angles.

• MACHINE SHOP

• At least one turning job is to be demonstrated.




Instructions for Laboratory

• The objective of the laboratory is learning. The experiments are designed to

illustrate phenomena in different areas of Workshop and to expose you to

uses of instruments. Conduct the job with interest and an attitude of learning.

• You need to come well prepared for the job.

• Work quietly and carefully (the whole purpose of experimentation is to

make reliable measurements!) and equally share the work with your

partners.

• All presentations of job and diagram should be neatly and carefully done.

• Diagrams should be neatly drawn with pencil. Always display units.

• Come equipped with scales, pencils etc.

• Do not fiddle idly with apparatus. Handle instruments with care. Report any

breakage to the Instructor. Return all the equipment you have signed out for

the purpose of your experiment.




CARPENTRY SECTION

The term carpentry is related to assembly of parts, after bringing the dimension or shape

to the required size or form, in order to secure the necessary fit. The operations required for the

same are usually carried out on a work bench, hence the term bench work is also added with the

name carpentry. The bench work and fitting plays an important role in engineering. Although in

today's industries most of the work is done by automatic machines which produces the jobs with

good accuracy but still it (job) requires some hand operations called carpentry operations. The

person working in the carpentry shop is called carpenter.

CARPENTRY TOOLS:

carpentry shop tools are classified as below:

• Work Holding Devices/ Clamping Tools.

• Measuring Tools.

• Marking Tools.

• Cutting Tools.

• Striking Tools.

• Drilling Tools.

• Planing Tools.

I. WORK HOLDING DEVICES /CLAMPING TOOLS:

1. Work Bench:

A carpentry process can be done at various

places, but most of the important operations of

fitting are generally carried out on a table called

work bench.

The work bench is a strong, heavy and rigid

table made up of hard wood.

The size of the work bench required is about 150

to 180 cm length, nearly 90 cm width and

approximately 76 to 84 cm height.



DMCE AIROLI/MECHANICAL ENGINEERING/BASIC WORKSHOP PRACTICE

2. CARPENTRY BENCH VICE:

It is firmly fixed to the bench with the help of nuts and bolts. It consists of a cast Iron body and

cast iron jaws. One jaw is fixed to the body and the second slides on a square threaded screw

with the help of a handle.

The jaws are opened as per vice

with the help of handle. Handle is used to move the movable jaw

3. BAR CLAMP:

It is used for holding wide work such as box of frame constructions and jointed broads. It

consists of a steel bar fitted with two jaws, one of which is movable by a screw and other is fixed

into one of the spaced holes by fastening pin.

4. C-CLAMP:

It is used for holding small work on the bench. It consists of a frame with a jaw at one end, and

movable jaw, which is operated by a screw and a thumb nut, at the other end.



ENGINEERING/BASIC WORKSHOP PRACTICE-I MANUAL/AY 201

BENCH VICE:



as per vice specification; job is placed in the two jaws and is fully tightened

with the help of handle. Handle is used to move the movable jaw


a steel bar fitted with two jaws, one of which is movable by a screw and other is fixed

into one of the spaced holes by fastening pin.


aw, which is operated by a screw and a thumb nut, at the other end.



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; job is placed in the two jaws and is fully tightened


a steel bar fitted with two jaws, one of which is movable by a screw and other is fixed





II. MEASURING TOOLS:

1. Steel Rule

It consist of a hardened steel strip having line graduation etched or engraved in it they are usually

150 mm or 300mm long and is used to take

These are marked in inches or millimeters. All the faces are machined true. The edges of steel

rule should be protected from rough handling

2. Calipers

These are generally used to measure the inside or outside diameters. Different types are:

i. Outside Caliper: It is used to measure the outside dimensions.

ii. Inside Caliper: It is used to measure the inside dimensions.

iii. Spring Caliper: Spring is provided to app

any desired position.

iv. Hermaphrodite, Jenny or Oddleg Caliper: One leg is bent at the tip inwardly and the other

has a straight pointed end. It is used to scribe lines parallel to the straight edges.





and is used to take linear measurement to an accuracy 1mm


rule should be protected from rough handling.


Outside Caliper: It is used to measure the outside dimensions.

Inside Caliper: It is used to measure the inside dimensions.

Spring Caliper: Spring is provided to apply the pressure and lock nut is provided to lock

Hermaphrodite, Jenny or Oddleg Caliper: One leg is bent at the tip inwardly and the other




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linear measurement to an accuracy 1mm or 0.5mm.



ly the pressure and lock nut is provided to lock

Hermaphrodite, Jenny or Oddleg Caliper: One leg is bent at the tip inwardly and the other





3. Vernier Caliper:

It is used for measuring the outer dimensions of round, flat, square components and also the

inner size of the holes and bore. A narrow blade is used to measure the depth of bar slots etc. The

reading accuracy in metric system is 0.02 mm

stainless steel.

III. MARKING TOOLS:

1. combination-square head:

A combination square is a tool

in woodworking, stonemasonry and

a ruler and one or more interchangeable

it. The most common head is the

used to lay out or check right and 45° angles

2. Carpenter's square:

The steel square is a tool used in

tools to lay out structures that are square (that is, built at

accurately measured right angles

of steel, but the name steel square

armed square that has additional uses for measurement,

especially of various angles. Today the steel square is more

commonly referred to as the framing square

square. It consists of a long, wider arm and a shorter,

narrower arm, which meet at an angle

angle). It can also be made of aluminum

The longer wider arm is two inches

one and a half inches wide, and is called the






reading accuracy in metric system is 0.02 mm and British system it is 0.001”. It is made of

tool used for multiple purposes

and metalworking. It is composed of

interchangeable heads that may be affixed to

mon head is the standard or square head which is

and 45° angles.

is a tool used in carpentry. Carpenters use various

tools to lay out structures that are square (that is, built at

right angles), many of which are made

steel square refers to a specific long-

armed square that has additional uses for measurement,

. Today the steel square is more

framing square or carpenters

. It consists of a long, wider arm and a shorter,

arm, which meet at an angle of 90 degrees (a right

luminum or polymers, which are light and resistant to rust.

inches wide, and is called the blade; the shorter narrower arm, is

one and a half inches wide, and is called the tongue. The square has many uses, including laying



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and British system it is 0.001”. It is made of

, which are light and resistant to rust.

; the shorter narrower arm, is

. The square has many uses, including laying




out common rafters, hip rafters and

octagonal scale. On the newer framing squares there are degree conversions for different pitches

and fractional equivalents.

3. Marking Gauge and Scriber

Marking gauge made from hard wood and i

Scriber is made up of high carbon steel and is hardened from the front edge. It is used for

marking of the lines.

4. Try Square:

It is used for checking squareness of two

consists of a blade made up of steel, which is attached to a

base at 90 degree. The base is made up of cast iron or

steel. It is also used to mark the right angles and

measuring straightness of surfaces. Never use try square

as a hammer.

METHOD OF MARKING

Marking means setting out dimensions with the help of a working drawing or directly

transferring them from a similar part. The procedure of marking is as follows:

1. The surface to be marked is

2. Then the work is held In a holding device depending upon shape

3. Lines in horizontal direction are scribed by means of a

angles can be drawn by try square

4. The centre on the end of a

gauge etc.

5. The circles and arcs on a flat surface are marked by means of a divider.




rafters and stairs. It has a diagonal scale, board foot

scale. On the newer framing squares there are degree conversions for different pitches

Scriber:

gauge made from hard wood and its scribing pin is made up of high carbon steel


It is used for checking squareness of two surfaces. It

consists of a blade made up of steel, which is attached to a

base at 90 degree. The base is made up of cast iron or

steel. It is also used to mark the right angles and

measuring straightness of surfaces. Never use try square


transferring them from a similar part. The procedure of marking is as follows:

The surface to be marked is smooth with the jack plane.

n a holding device depending upon shape

Lines in horizontal direction are scribed by means of a marking gauge. Lines at right

try square and then using the scriber, If true surface is available

The centre on the end of a wood log can be located by using an odd leg caliper, surface

The circles and arcs on a flat surface are marked by means of a divider.



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board foot scale and an

scale. On the newer framing squares there are degree conversions for different pitches

is made up of high carbon steel.



gauge. Lines at right

If true surface is available.

can be located by using an odd leg caliper, surface




IV. CUTTING TOOLS

1. Saw

Saw is used for cutting of wood. It consists of a handle, which is

made from wood, plastic or aluminum. The blade is made up of

high carbon steel or spring steel.

The points of the teeth are bent in a zig-zag fashion, to cut a wide

groove and prevent the body of the blade from rubbing or jamming

in the saw cut. The teeth of the blades are generally forward cut so

in the case, pressure is applied in the forward direction only.

Depending upon the direction of cut, blades are classified as:

• Forward cut

• Backward cut.

CROSS CUT SAW:

It is used for cutting the wood across the grains (Hand saw). Its teeth are pointed. The pitch of

the teeth is about 2.5 to 3.0mm and blade length is about 600mm. Its teeth have less ‘set’ than the

rip saw.

RIP SAW:

It is used for cutting the wood along the grains. Its teeth have chisel edge. The pitch of the teeth

is about 5 to 8mm and length of the blade is about 700mm.The process of cutting the wood along

the grains is called ripping. Because of high flexibility of the blade and also number of cutting

points per cm (i.e., high pitch) it is not suitable for cutting across the grains.

TENON SAW:

Tenon saw or back saw is used for cutting small work. It is mostly adapted in joint work. It has a

brass or steel back which strengthens the blade, but it restricts the depth of cut. Its fine teeth (6 to

8teeth/cm) and stiff back permits the smooth, accurate cutting for marking joints. The saw is

available in different length ranging from 250 to 400 mm.

INSIDE CHISEL:

It is leveled inside and is used for marking curved profiles.




PLANNING TOOLS:

Planning tools are used for reducing and smoothing the surface.

WOODEN JACK PLANE:

It consists of a wooden body or stocks in which blade or stock cutter is fastened at an angle of

45° to the sole. The plane is on (blade or cutter) and the cap iron (back iron) is assembled and

assembly is inserted in the mouth of plane along with the wedge. The back iron supports the

cutting edge and also breaks the shavings so that they air away from the blade. The blade can be

set for taking deeper or shallower cuts. The length of the jack plane is about 350to 425mm. The

blade is made of high carbon steel and has a width of 50 to 75 mm. Its cutting edge is tempered

and ground to an angle of 25 to 30° and it is slightly curved (Convex).

METAL JACK PLANE:

Its body is made of gray cast iron and it is provided with a wooden handle at the back and a

wooden knob at the front for holding with both the hands. A fine screw is used for adjusting the

depth of cut i.e.; the thickness of shaving removed and a level is used for lateral adjustment of

the blade. It is very durable and gives better finish.

CHISELS:

Chisels are used for cutting excess wood in shaping and joint making.

FIRMER CHISEL:

The firmer chisel is capable of doing heavy work and is used for jointing and shaping the wood,

with or without mallet. The chisel blade is made of rectangular section with beveled edge length

of the blade is about 125mm and the width of the edge varies from 3 to 5mm.

DOVETAIL CHISEL:

It is similar to firmer chisel but sides are leveled so that it can cut sharp corners. It is used for

cutting sockets where the angles are less than a right angle.

MORTISE CHISEL:

These chisels are robust, and can withstand heavy blows. It has a thick stock and narrow cutting

edge. It is used for cutting mortises, and its width is ground to exact size of mortise to be out.

OUTSIDE CHISEL:

It is level on outside and it is used for making hallows.




STRIKING TOOLS:

Striking tools are used to drive in nails and to operate chisels.

WARRINGTON HAMMER:

It is mostly used for bench work and light work. It is made of cast steel

peen. The wooden handle fits in the eye and steel wedge is driven in to form a rigid joint.

CLAW HAMMER:

It is dual purpose hammer. It has a hammer face which is used to drive in nails, and claw at the

other end for pulling out nails from the wood. It is designed by its weight and it varies from 375

to 675gms.

MALLET:

It is used for operating the chisels

handle. The striking faces are made flat, and may be in square or rectangular cross

DRILLING & BORING TOOLS:

These tools are used for drilling and making holes in wooden jobs.

GIMLET:

It is hand operated tool used for making small holes for screws. It has a spiral flutes with screw

like point.




TYPES OF PLANES

Striking tools are used to drive in nails and to operate chisels.

It is mostly used for bench work and light work. It is made of cast steel with tempered face and




It is used for operating the chisels and gauges. It is made of hard wood and is provided with

handle. The striking faces are made flat, and may be in square or rectangular cross

DRILLING & BORING TOOLS:

These tools are used for drilling and making holes in wooden jobs.

is hand operated tool used for making small holes for screws. It has a spiral flutes with screw



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with tempered face and




and gauges. It is made of hard wood and is provided with

handle. The striking faces are made flat, and may be in square or rectangular cross-section.

is hand operated tool used for making small holes for screws. It has a spiral flutes with screw




HAND DRILLS:

It is used for drilling small holes. A straight shank drill is used with this tool. It is small, light in

weight. The bit is clamped in the chuck at its end.

AUGER:

It is used for producing long deep holes. It is a steel bar with an eye at the top in which a handle

is fitted. The bottom end is provided with a screw point.

HAND DRILL

MISCELLANEOUS TOOLS:

SCREW DRIVER:

These are used for driving the screws on the board i.e., wood or unscrewing them from wood.

The size is specified by the length of the blade.

WOOD RASP FILE:

It is exclusively used for finishing the wood surface. It has sharp cutting teeth and it is used for

finishing small curved surfaces.

PINCER:

It is used for pulling out nails and is more efficient then the claw hammer





in the chuck at its end.


is fitted. The bottom end is provided with a screw point.

AUGER BIT

GIMLET

MISCELLANEOUS TOOLS:


The size is specified by the length of the blade.


It is used for pulling out nails and is more efficient then the claw hammer



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AUGER BIT






SCREW DRIVER PINCER

WOOD RASP FILE

WOOD WORKING MACHINE ALL IN ONE




WOOD TURNING:

Woodturning is the craft of using the wood lathe with hand-held tools to cut a shape that is

symmetrical around the axis of rotation. Like the potter's wheel, the wood lathe is a simple

mechanism which can generate a variety of forms. The operator is known as a turner, and the

skills needed to use the tools were traditionally known as turnery. In pre-industrial England,

these skills were sufficiently difficult to be known as 'the misterie' of the turners guild. The skills

to use the tools by hand, without a fixed point of contact with the wood, distinguish woodturning

and the wood lathe from the machinists lathe, or metal-working lathe.

Items made on the lathe include tool handles, candlesticks, egg cups, knobs, lamps, rolling pins,

cylindrical boxes, Christmas ornaments, bodkins, knitting needles, needle cases, thimbles, pens,

chessmen, spinning tops; legs, spindles and pegs for furniture; balusters and newel posts for

architecture; baseball bats, hollow forms such as woodwind musical instruments, urns,

sculptures; bowls, platters, and chair seats. Industrial production has replaced many of these

products from the traditional turning shop. However, the wood lathe is still used for

decentralized production of limited or custom turnings. A skilled turner can produce a wide

variety of objects with five or six simple tools. The tools can be reshaped easily for the task at

hand.

WOOD TURNING MACHINE WOOD TURNING TOOLS




WOOD TURNING / PLANING SHAPES




WELDING SECTION

INTRODUCTION

Welding is the process of joining similar metals by the application of heat, with or without

application of pressure or filler metal, in such a way that the joint is equivalent in composition

and characteristics of the metals joined. In the beginning, welding was mainly used for repairing

all kinds of worn or damaged parts. Now, it is extensively used in manufacturing industry,

construction industry (construction of ships, tanks, locomotives and automobiles) and

maintenance work, replacing riveting and bolting, to a greater extent.

The various welding processes are:

1. Electric arc welding,

2. Gas welding

3. Thermal welding

4. Electrical Resistance welding and

5. Friction welding

However, only electric arc welding process is discussed in the subject point of view.

Electric arc welding Arc welding is the welding process, in which heat is generated by an electric arc struck between

an electrode and the work piece. Electric arc is luminous electrical discharge between two

electrodes through ionized gas.

Any arc welding method is based on an electric circuit consisting of the following parts: a. Power supply (AC or DC);

b. Welding electrode;

c. Work piece;

d. Welding leads (electric cables) connecting the electrode and work piece to the power

supply. Electric arc between the electrode and work piece closes the electric circuit. The arc

temperature may reach 10000°F (5500°C), which is sufficient for fusion the work piece edges

and joining them. When a long joint is required the arc is moved along the joint line. The front

edge of the weld pool melts the welded surfaces when the rear edge of the weld pool solidifies

forming the joint. Transformers, motor generators and rectifiers’ sets are used as arc welding

machines. These machines supply high electric currents at low voltage and an electrode is used

to produce the necessary arc. The electrode serves as the filler rod and the arc melts the surface

so that, the metals to be joined are actually fixed together.

Sizes of welding machines are rated according to their approximate amperage capacity at 60%

duty cycle, such as 150,200,250,300,400,500 and 600 amperes. This amperage is the rated

current output at the working terminal.




Transformers

The transformers type of welding machine produces A.C current and is considered to be the least

expensive. It takes power directly from power supply line and transforms it to the voltage

required for welding. Transformers are available in single phase and three phases in the market.

Motor generators

These are D.C generators sets, in which electric motor and alternator are mounted on the same

shaft to produce D.C power as pert the requirement for welding. These are designed to

produce D.C current in either straight or reversed polarity. The polarity selected for welding

depends upon the kind of electrode used and the material to be welded.

Rectifiers

These are essentially transformers, containing an electrical device which changes A.C into D.C

by virtue of which the operator can use both types of power (A.C or D.C, but only one at a

time).In addition to the welding machine; certain accessories are needed for carrying out the

welding work.

Welding cables

Two welding cables are required, one from machine to the electrode holder and the other,

from the machine to the ground clamp. Flexible cables are usually preferred because of the case

of using and coiling the cables. Cables are specified by their current carrying capacity,

say 300 A, 400 A, etc.

Fig 1.1: The Basic circuit for arc welding




Fig 1.2: Schematic diagram of shielded metal arc welding

Fig 1.3: Schematic diagram of gas metal arc welding

Electrodes

Filler rods are used in arc welding are called electrodes. These are made of metallic wire called

core wire, having approximately the same composition as the metal to be welded. These are coated

uniformly with a protective coating called flux. While fluxing an electrode; about 20mm of length is left

at one end for holding it with the electrode holder. It helps in transmitting full current from electrode

holder to the front end of the electrode coating. Flux acts as an insulator of electricity. In general,

electrodes are classified into five main groups; mild steel, carbon steel, special alloy steel, cast iron and

non‐ferrous. The greatest range of arc welding is done with electrodes in the mild steel group. Various

constituents like titanium oxide, potassium oxide, cellulose, iron or manganese, Ferro silicates,

carbonates, gums, clays, asbestos, etc., are used as coatings on electrodes. While welding, the coating or

flux vaporizes and provides a gaseous shield to prevent atmospheric attack. The size of electrode is




measured and designated by the diameter of the core wire in SWG and length, apart from the brand and

code names; indicating the purpose for which there are most suitable

Electrodes may be classified on the basis of thickness of the coated flux. As

1. Dust coated or light coated

2. Semi or medium coated and

3. Heavily coated or shielded

Electrodes are also classified on the basis of materials, as

1. Metallic and

2. Non‐metallic or carbon

Metallic arc electrodes are further sub‐divided into

1. Ferrous metal arc electrode (mild steel, low/medium/high carbon steel, cast iron, stainless steel )

2. Non‐ferrous metal arc electrodes (copper, brass, bronze, aluminum, etc). In case of non‐metallic arc

electrodes, mainly carbon and graphite are used to make the electrodes.

Electrode holder Ground Clamp

Wire brush Chipping hammer




Hand gloves

WELDING TOOLS

Electrode holder The electrode holder is connected to the end of the welding cable and holds the electrode. Itshould be

light, strong and easy to handle and should not become hot while in operation. Figure shows one type of

electrode holder. The jaws of the holder are insu

Ground clamp It is connected to the end of the ground cable and is clamped to the work or welding table to complete the

electric circuit. It should be strong and durable and give a low resistance connection.

Wire brush and chipping hammer

A wire brush is used for cleaning and preparing the work for welding. A chipping hammer is used for

removing slag formation on welds. One end of the head is sharpened like a cold chisel and the other, to a

blunt, round point. It is generally made of tool steel. Molten metal disperse

the form of small drops, is known as spatter. When a flux coated electrode is used in welding process,

then a layer of flux material is formed over the welding bead which contains the impurities of weld

material. This layer is known as slag. Removing the spatter and slag formed on and around the welding

beads on the metal surface is known as chipping.

Welding table and cabin It is made of steel plate and pipes. It is used for positioning the parts to be welded properly.

Welding cabin is made‐up by any suitable thermal resistance material, which can isolate the surrounding

by the heat and light emitted during the welding process. A suitable draught should also be provided for

exhausting the gas produced during welding.

Face shield A face shield is used to protect the eyes and face from the rays of the arc and from spatter or

flying particles of hot metal. It is available either in hand or helmet type. The hand type is convenient to

use wherever the work can be done with o

leaves both hands free for the work. Shields are made of light weight non

dark glasses to filter out the Harmful rays of the arc. In some designs, a cover glass is fi

dark lens to protect it from spatter.

Hand gloves These are used to protect the hands from electric shocks and hot spatters




Face shield

The electrode holder is connected to the end of the welding cable and holds the electrode. Itshould be


electrode holder. The jaws of the holder are insulated, offering protection from electric shock.

It is connected to the end of the ground cable and is clamped to the work or welding table to complete the

electric circuit. It should be strong and durable and give a low resistance connection.

Wire brush and chipping hammer eaning and preparing the work for welding. A chipping hammer is used for


blunt, round point. It is generally made of tool steel. Molten metal dispersed around the welding heads, in



s known as slag. Removing the spatter and slag formed on and around the welding

beads on the metal surface is known as chipping.

It is made of steel plate and pipes. It is used for positioning the parts to be welded properly.

up by any suitable thermal resistance material, which can isolate the surrounding


exhausting the gas produced during welding.

A face shield is used to protect the eyes and face from the rays of the arc and from spatter or


use wherever the work can be done with one hand. The helmet type though not comfortable to wear,

leaves both hands free for the work. Shields are made of light weight non‐reflecting fiber and fitted with

dark glasses to filter out the Harmful rays of the arc. In some designs, a cover glass is fi

These are used to protect the hands from electric shocks and hot spatters



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The electrode holder is connected to the end of the welding cable and holds the electrode. Itshould be


lated, offering protection from electric shock.

It is connected to the end of the ground cable and is clamped to the work or welding table to complete the

eaning and preparing the work for welding. A chipping hammer is used for


d around the welding heads, in



s known as slag. Removing the spatter and slag formed on and around the welding

It is made of steel plate and pipes. It is used for positioning the parts to be welded properly.

up by any suitable thermal resistance material, which can isolate the surrounding


A face shield is used to protect the eyes and face from the rays of the arc and from spatter or


ne hand. The helmet type though not comfortable to wear,

reflecting fiber and fitted with

dark glasses to filter out the Harmful rays of the arc. In some designs, a cover glass is fitted in front of the




TECHNIQUES OF WELDING

WELDING POSITIONS Depending upon the location of the welding joints, appropriate

hand movement is selected. The figure shows different welding positions.

Flat position welding In this position, the welding is performed from the upper side of the joint, and the face of the weld is

approximately horizontal. Flat welding is the preferred term; however, the same position is sometimes

called down hand.

Horizontal position welding In this position, welding is performed on the upper side of an approximately horizontal surface

and against an approximately vertical surface.

Vertical position welding In this position, the axis of the weld is approximately vertical as shown in figure.

Overhead position welding

In this welding position, the welding is performed from the unde




Depending upon the location of the welding joints, appropriate position of the electrode and

hand movement is selected. The figure shows different welding positions.

In this position, the welding is performed from the upper side of the joint, and the face of the weld is

al. Flat welding is the preferred term; however, the same position is sometimes

In this position, welding is performed on the upper side of an approximately horizontal surface

and against an approximately vertical surface.

In this position, the axis of the weld is approximately vertical as shown in figure.

In this welding position, the welding is performed from the underside of a joint

Weld positions



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position of the electrode and

In this position, the welding is performed from the upper side of the joint, and the face of the weld is

al. Flat welding is the preferred term; however, the same position is sometimes

In this position, welding is performed on the upper side of an approximately horizontal surface







WELDING JOINTS



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INTRODUCTION

In a machine shop, metals are cut to shape on different machine tools. A lathe is used to cut and

shape the metal by revolving the work against a cutting tool. The

chuck, fitted on to the lathe spindle or in

post, mounted on a movable carriage that is positioned on the lathe bed. The cutting tool can be

fed on to the work, either len

counter‐clockwise direction, when viewed from the tail stock end.

PRINCIPAL PARTS OF A LATHE

Figure 4.1 shows a center lathe, indicating the main parts. The name is due to the fact that

workpieces are held by the centers.

BED

It is an essential part of a lathe, which must be strong and rigid. It carries all parts of the

machine and resists the cutting forces. The carriage and the tail stock move along the guide ways

provided on the bed. It is usually made of cast iron.

HEAD STOCK

It contains either a cone pulley or gearings to provide the necessary range of speeds and feeds.It

contains the main spindle, to which the work is held and rotated.

TAIL STOCK




MACHINE SHOP


shape the metal by revolving the work against a cutting tool. The work is clamped either in a

chuck, fitted on to the lathe spindle or in‐between the centers. The cutting tool is fixed in a tool


fed on to the work, either lengthwise or cross‐wise. While turning, the chuck rotates in

clockwise direction, when viewed from the tail stock end.

RINCIPAL PARTS OF A LATHE


workpieces are held by the centers.


e cutting forces. The carriage and the tail stock move along the guide ways

provided on the bed. It is usually made of cast iron.


main spindle, to which the work is held and rotated.



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work is clamped either in a

between the centers. The cutting tool is fixed in a tool


wise. While turning, the chuck rotates in



e cutting forces. The carriage and the tail stock move along the guide ways





It is used to support the right hand end of a long work piece. It may be clamped in any position

along the lathe bed. The tail stock spindle has an internal Morse taper to receive the dead center

that supports the work. Drills, reamers, taps may also be fitted into the spindle, for performing

operations such as drilling, reaming and tapping.

CARRIAGE OR SADDLE

It is used to control the movement of the cutting tool. The carriage assembly consists of the

longitudinal slide, cross slide and the compound slide and apron. The cross slide moves across

the length of the bed and perpendicular to the axis of the spindle. This movement is used for

facing and to provide the necessary depth of cut while turning. The apron, which is bolted to the

saddle, is on the front of the lathe and contains the longitudinal and cross slide controls.




COMPOUND REST

It supports the tool post. By swiveling the compound rest on the cross slide, short tapers may be

turned to any desired angles.

TOOL POST

The tool post holds the tool holder or the tool, which may be adjusted to any working position.

LEAD SCREW

It is a long threaded shaft, located in front of the carriage, running from the head‐stock to the

tail stock. It is geared to the spindle and controls the movement of the tool, either for automatic

feeding or for cutting threads.

CENTERS

There are two centers known as dead center and live center. The dead center is positioned in

the tail stock spindle and the live center, in the head‐stock spindle. While turning between

centers, the dead center does not revolve with the work while the live center revolves with the

work.




WORK‐HOLDING DEVICES

1. THREE JAW CHUCK

It is a work holding device having three jaws (self‐centering) which will close or open with

respect to the chuck center or the spindle center, as shown in figure. It is used for holding regular

objects like round bars, hexagonal rods, etc.

FACE PLATE

It is a plate of large diameter, used for turning operations. Certain types of work that cannot be

held in chucks are held on the face plate with the help of various accessories.

LATHE DOGS AND DRIVING PLATE

These are used to drive a work piece that is held between centers. These are provided with an

opening to receive and clamp the work piece and dog tail, the tail of the dog is carried by the pin

provided in the driving plate for driving the work piece.

MEASURING INSTRUMENTS

1. OUTSIDE AND INSIDE CALIPERS

Firm joint or spring calipers are used for transfer of dimensions with the help of a steel rule.




2. VERNIER CALIPERS

Vernier caliper is a versatile instrument with which both outside and inside measurements may

be made accurately. These instruments may have provision for depth measurement also.

3. MICROMETERS

Outside and inside micrometers are used for measuring components where greater accuracy is

required.

CUTTING PARAMETERS

1. CUTTING SPEED

It is defined as the speed at which the material is removed and is specified in meters per

minute. Ti depends upon the work piece material, feed, depth of cut, type of operation and so

many other cutting conditions. It is calculated from the relation, Spindle speed (RPM) =

cutting speed x 1000 / (πD) Where D is the work piece diameter in mm.

2. FEED

It is the distance traversed by the tool along the bed, during one revolution of the work. Its value

depends upon the depth of cut and surface finish of the work desired.

3. DEPTH OF CUT

It is the movement of the tip of the cutting tool, from the surface of the work piece and

perpendicular to the lathe axis. Its value depends upon the nature of operation like rough turning

or finish turning.




TOOL MATERIALS

General purpose hand cutting tools are usually made from carbon steel or tool steel. The single

point lathe cutting tools are made of high speed steel (HSS).the main alloying elements in 18‐4‐1

HSS tools are 18 percent tungsten, 4 percent chromium and 1 percent vanadium.5 to 10 percent

cobalt is also added to improve the heat resisting properties of the tool.

Carbide tipped tools fixed in tool holders, are mostly used in production shops.

LATHE OPERATIONS

1. TURNING

Cylindrical shapes, both external and internal, are produced by turning operation. Turning is the

process in which the material is removed by a traversing cutting tool, from the surface of a

rotating workpiece. The operation used for machining internal surfaces is often called the boring

operation in which a hole previously drilled is enlarged. For turning long work, first it should be

faced and center drilled at one end and then supported by means of the tail‐stock centre.

2.BORING

Boring is enlarging a hole and is used when correct size drill is not available. However, it should

be noted that boring cannot make a hole.

3.FACING

Facing is a machining operation, performed to make the end surface of the work piece, flat and

perpendicular to the axis of rotation. For this, the work piece may be held in a chuck and rotated

about the lathe axis. A facing tool is fed perpendicular to the axis of the lathe. The tool is slightly

inclined towards the end of the work piece.




4.TAPER TURNING

A taper is defined as the uniform change in the diameter of a work piece, measured along its

length. It is expressed as a ratio of the difference in diameters to the length. It is also expressed in

degrees of half the included (taper) angle. Taper turning refers to the production of a conical

surface, on the work piece on a lathe. Short steep tapers may be cut on a lathe by swiveling the

compound rest to the required angle. Here, the cutting tool is fed by means of the compound

slide feed handle. The work piece is rotated in a chuck or face plate or between centers.

5.DRILLING

Holes that are axially located in cylindrical parts are produced by drilling operation, using a twist

drill. For this, the work piece is rotated in a chuck or face plate. The tail stock spindle has a

standard taper. The drill bit is fitted into the tail stock spindle directly or through drill chuck. The

tail stock is then moved over the bed and clamped on it near the work. When the job rotates, the

drill bit is fed into the work by turning the tail stock hand wheel.

6.KNURLING

It is the process of embossing a diamond shaped regular pattern on the surface of a work piece

using a special knurling tool. This tool consists of a set of hardened steel rollers in a holder with

the teeth cut on their surface in a definite pattern. The tool is held rigidly on the tool post and the

rollers are pressed against the revolving work piece to squeeze the metal against the multiple

cutting edges. The purpose of knurling is to provide an effective gripping surface on a work

piece to prevent it from slipping when operated by hand.

7.CHAMFERING

It is the operation of beveling the extreme end of a work piece. Chamfer is provided for better

look, to enable nut to pass freely on threaded work piece, to remove burrs and protect the end of

the work piece from being damaged.

8.THREADING

Threading is nothing but cutting helical groove on a work piece. Threads may be cut either on

the internal or external cylindrical surfaces. A specially shaped cutting tool, known as thread

cutting tool, is used for this purpose. Thread cutting in a lathe is performed by traversing the

cutting tool at a definite rate, in proportion to the rate at which the work revolves.

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