Grinding & finishing - 2

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Department of Technical Education

Andhra PradeshName : V. Yesu prasada Rao

Designation : Senior LecturerBranch : Mechanical Engineering

Institute : M.B.T.S Govt polytechnic,Guntur

Year/semister : IV Semister

Subject : Manufacturing technology IISubject code : M402

Topic : Grinding & Finishing processes

Duration : 50 Min

Subtopic : Bonds and Bonding processes

Teaching Aids : Diagrams & ppt

Revised by : K.Chakravarty


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Recap

In the last class,you have learnt about

Grinding

Principle of Grinding

Abrasives

Types of abrasives


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Objectives

On completion of this period you would be able

to know about

The bonding materials

Bonding processes


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The Cutting Action of Abrasive Grains


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Elements of Grinding Wheel

Abrasives

Bond

voids


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Bond Materials

Bonding materials are used for holding the abrasivegrains together

Commonly used Bond materials for different bonds are

Bonds Bonding materials1. Vitrified bond clay (or) feldspar

2. Silicate bond silicate soda

3. Shellac bond shellae

4. Rubber bond pure rubber

5. Bakelite synthetic resins (bakellite)


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Vitrified Bond Grinding Wheels

Fig.2


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Bonding processes

Vitrified Bond:-

Vitrified bond is made of clay or field spar

The clay and water is mixed with abrasive and the

mixture is moulded to form wheels Then it is baked in kiln up to a temp of 12500c to develop

structural strength

Vitrified bond is denoted by v

Vitrified bond has high strength and porosity These wheels posses low bending strength


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Vitrified Bond

Vitrified Bond offers good

strength to wheels

It gives good porosity to allow

high stock removal with cool

cutting It is effected by heat, cold,

water, acids or oils etc

75% of wheels now

manufactured are made withthis method

Fig.3


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Bonding Processes - Silicate Bond

Silicate Bond is made from silicate soda and is

mixed with abrasive grains

The mixture is moulded to wheel shape and thenbaked in furnace at a temperature of 2600c for

several days


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Bonding Processes - Silicate Bond

Silicate wheels are water

proof

It can be used where

machining with coolent is

performed

Used in making large wheels

Fig.5


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Bonding Processes - Shellac Bond

It is Elastic Bond

Shellac is mixed with abrasive in a heated container and

is shaped in a heated mould

The shaped wheels are then baked at 1500c for several

hours

It is denoted by E

Shellac wheels are capable of producing high surface

finish


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Shellac Bond Grinding Wheel

Fig.6


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Bonding Processes - Shellac Bond

It is used for chilled cast

iron. Steel rolls, hardened

steel cams and aluminiumpistons

It is not intended for heavy

duty

Fig.7


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Bonding Processes - Rubber Bonds

Are made from pure

rubber and abrasive

Abrasive skins are mixed

with pure rubber andsulphur (as a vulconiser )

The above mixture is

deformed into sheets

Fig.8


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Bonding Processes - Rubber Bond

Rubber bonded wheels are strongest of all and tough

These wheels produce high surface finish

These are affected by alkaline solution

These are suitable for making externally thin wheels, forfinishing ball bearing

Can also be used as regulating wheels in centre less

grinding

Denoted by letter R


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Bonding Processes - Bakelite (or) Resinoid

Bond

Are produced by mixing abrasive grains with synthetic

resins and other components

The mixture is placed in moulds and heated at about

2000c

At this temperature , the resin gets to hold the abrasive

grains in the wheel form


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Resinoid Bond Grinding Wheels

Fig.9


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Bakelite (or) Resinoid Bond

These are flexible and can run very fast

Used to remove large stock

Water base cutting fluids can be used as coolants

Denoted by letter B

Used for precision grinding cams and rolls requiring high

finish


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Summary

In this class we have learnt about

Type of bond material

Process of making wheels with different bond material

and characteristics

The applications of bond materials


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Quiz

(1) Clay (or) feldspar based bond material is known as

(a) Vitrified bond

(b) Resinoid Bond (or) Bakelite

(c) Oxy-Chloride Bond

(d) Rubber Bond


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Frequently Asked Questions

(1) Explain briefly about :

(a) Silicate Bond

(b) Rubber Bond

(c) Bakelite Bond (or) Resinoid Bond

Grinding & finishing - 2

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