SHREE S’AD VIDYA MANDAL INSTITUTE OF TECHNOLOGY

Prepared By:- Prajapati Urvesh

Mirza Hamza

Patel mo.Kamil

Department:- Mechanical-C

Semester:- 3rd Sem

PRESENTETION ONGRINDING

Contents

1. Introduction

2. Principle of Grinding Machine

3. Types of grinding

4. Various elements of grinding wheel

5. Shapes and Coding of a Grinding Wheel

6. Wheel surface finishing

7. Classification of Grinding Machines

1. Introduction Grinding is a metal cutting operation performed by means of abrasive particles rigidly mounted on a rotating wheel. Each of the abrasive particles act as a single point cutting tool and grinding wheel acts as a multipoint cutting tool. The grinding operation is used to finish the workpieces with extremely high quality of surface finish and accuracy of shape and dimension. Grinding is one of the widely accepted finishing operations because it removes material in very small size of chips 0.25 to 0.50 mm. It provides accuracy of the order of 0.000025 mm.

2. Principle of Grinding Machines

Work piece is fed against the rotating abrasive wheel.Due to action of rubbing or friction between the

abrasive particles and work piece material is removed.

3. Types of Grinding

On the basis of quality of grinding, it is classified as rough grinding and precision grinding. Rough Grinding Precision Grinding

Rough Grinding:-

It involves removal of stock without any reference to the accuracy of results.

Precision Grinding:-

Precision grinding removes negligible amount of metal. It is used to produce finished parts and accurate dimensions.

4. Various elements of a Grinding Wheel

The various main elements of a grinding wheel are abrasive; bonds and structure which are described below.

Abrasive:- Generally abrasive properties like hardness, toughness and resistance to fracture uniformly abrasives are classified into two principal groups:- Natural abrasives Artificial abrasive

Natural abrasive:- There are a few examples of natural abrasives which include sand stone (solid quartz), emery, & diamond.

Artificial abrasive:- Main artificial abrasive are silicon carbide and aluminium oxide. Artificial abrasive are preferred in manufacturing of grinding wheels because of their uniformity and purity.

NATURAL ABRASIVE ARTIFICIAL ABRASIVE

Bond:- A bond is an adhesive material used to held abrasive particles together relatively stable that constitute a

grinding wheel.

Different types of bonds are:-

(a) Vitrified bond

(b) Silicate bond

(c) Shellac bond

(d) Resinoid bond

(e) Rubber bond

(f) Oxychloride bond

(a) Vitrified bond:-

This bond consists of mixture of clay and water. Clay and abrasives are thoroughly mixed with water to make a uniform mixture. This bond is denoted by symbol ‘V’ in specification.

(b) Silicate bond:-

Silicate bonds are made by mixing abrasive particles with silicate and soda or water glass.These wheels are denoted by ‘S’ in specification.

(c) Shellac bond:-

These are prepared by mixing abrasive with shellac than moulded by rolling and pressing and then by heating up to 150` C for several hours. This bond is denoted by ‘E’ in specifications.

(d) Resinoid bond:-

These bonds are prepared by mixing abrasives with synthetic resins like backelite and redmanol and other compounds & baked up to 200` C. A Resinoid bond is denoted by the letter ‘B’.

(e) Rubber bond:-

Rubber bonded wheels are made by mixing abrasives with pure rubber and sulphur.A rubber wheel bonded wheel is denoted by the letter ‘R’.

(f) Oxychloride bond:-

These bonds are processed by mixing abrasives with oxides and chlorides of magnesium. An oxychloride bonded wheel is specified the letter ‘O’.

STRUCTURE OF GRINDING WHEEL

5. Shapes and Coding of a Grinding Wheel

Shapes:-

There are different shapes of grinding wheel

which mention below.

Straight Wheel:- These are generally used for cylindrical, internal, centreless and surface grinding operations. These wheels vary in size, diameter and width of the face.

Tapered Face Straight Wheels:- It is also a straight wheel but its free is slightly tapered to facilitate the grinding of threads an gear teeth.

Cylindrical Wheel Ring:- It is used for surface grinding, i.e. production of flat surfaces. Grinding takes place with the help of face of the wheel.

Cup Wheel:- It is used for grinding flat surfaces with the help of face of grinding wheel.

Flaring Cup Wheel:- It is used in grinding of tools in tool room.

Saucer Wheel:- It is used for sharpening of circular or band saw.

Segmented Wheel:- These are normally on vertical spindle, rotary type and reciprocating type surface grinders.

Dish Wheel:- It is used for grinding of tools in tool room. It is capable to grind very narrow places due to its thinners.

Coding:-

The Indian Standard Coding system of grinding wheel is IS : 551-1954. It gives a general indication of the hardness and abrasive size of any wheel as compared with another.

Coding of a grinding wheel consists of six symbols as described below.

W : Symbol for Manufacturer’s Abrasive Type (Prefix)

C : Name of Abrasive

30 : Grain Size

L : Grade

5 : Structure Type

R : Bond Type

17 : Manufacturer Symbol for Record (Suffix)

The sequence of codes of a grinding should be followed in the same sequence as described above Their brief description is given below.

Prefix:- Manufacturer’s Symbol.

Abrasive:- Types of abrasive used in Grinding Wheel.

i.e. A= Aluminium Oxide

C= Silicon Carbide

Grain Size:- It affects the metal removal rate & finishing of surface.

Coarse Medium Fine Very fine

10 30 80 220

12 36 100 240

14 46 120 280

16 54 150 320

Grade:- Ability of bonding material to sustain abrasive.

Structure:- Structure between bonding material & abrasive grain inside the grinding wheel.

Dense Open

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Very soft A,B,C,D,E,F,G

Soft H,I,J,K

Medium L,M,N,O

Hard P,Q,R,S

Very hard T,U,V,W,X,Y,Z

`

Types of Bond:- It shows which type of bonding material is used.

V= Vitrified Bond

B= Resinoid Bond

R= Rubber Bond

E= Shellac Bond

S= Silicate Bond

Suffix:- Manufacturer’s own identification

Example of Coding

51A 36L5V23

• 51 = Manufacture’s symbol• A = Abrasive ( Aluminum Oxide)• 36 = Grain size (Medium)• L = Grade (Medium)• 5 = Structure ( Dense)• V = Bond type (Vitrified Bond)• 23 = Manufacture’s identification.

6. Wheel Surface Finishing

Glazing:-

This is the effect when the abrasive have become dull & ground to the ground. It is a condition in which cutting edge take glass-like appearance. This occurs due to high speed or the tool is very hard. To avoid glazing use softer wheel or decrease speed of wheel.

Loading:-

When the material of the work piece is filled the gap between the abrasive grain then it is called as loading. This material prevent the wheel from cutting freely. It may caused be grinding a soft material or by using a heel of too hard and running it too slowly.

Truing:-

It is a process of changing the shape of grinding wheel. It can be done on the new wheel or on the used tool. This is done to make tool true and equal distance from the center.

1. LOADING 2. GLAZING

Dressing:-

This is done on loaded and glazed tool to gain there sharp abrasive particles.

This is done using different types of dresser,o Metal crushero Diamond dressero Abrasive sticks/wheels.

7. Classification Of Grinding Machine

Grinding Machines are classified as,

a. Bench grinding machine

b. Surface grinding machine

c. Cylindrical grinding machine

d. Center less grinding machine

e. Internal grinding machine

f. Special purpose grinding machine

a. Bench grinding machine These types of grinding machine is used to hand grind cutting tools and perform rough grinding. It may be used for sharpening cutting tool such as lathe tools or drill bits.

b. Surface grinding machine

It is machine basically used to grind flat surface. Job is mounted to a table which moves longitudinally

as well as in transverse direction.Manual feed or power feed.Work piece can clamped in two ways–Manual clamps.–Magnetic chuck.

Internal pump and piping arrangement for coolant.Protective guard for safety.

Surface Grinding Machine

c. Cylindrical grinding machine

It is a process of grinding curved surfaces. Surface may be straight or tapered. Work piece is mounted on two centers, one is

tailstock centre and the other is headstock centre. Head stock center may or may not revolve.

WORKING PRINCIPLE

CYLINDRICAL GRINDING MACHINE

d. Centre less grinding machine

It is used to grind curved surface work piece which are long and slender.

Work piece rests on a work-rest blade and is backed by a second wheel called as regulating wheel.

Grinding wheel pushes the work piece down the work-rest blade against the regulating wheel.

WORKING PRINCIPLE

CENTERLESS GRINDING MACHINE

e. Internal grinding machine

In this type the grinding is done in the internal side of work piece.

In this operation the work piece may rotate or may not be rotate.

It can be done on different internal surface like straight, tapered, grooved, or profile.

WORKING PRINCIPLE

f. Some special grinding

It uses the principle of cylindrical grinding. Mainly it used for threaded profile. Specially formed wheel is use A single ribbed or multy ribbed wheel can be

used as shown in fig.

SOME SPECIAL GRINDING

THANK YOU