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Grinding
Grinding is a surface finishing operation
where very thin layer of material is removed
in the form of dust particles.
 Thickness of material removed is in range of
0.25 to 0.50 mm.
 Tool used is a abrasive wheel.

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Abrasives
Abrasive is the material employed for
sharpening, grinding and polishing
operations.
 Natural abrasive – emery, corundum,
quartz, sandstone, diamond, etc.
 Artificial abrasive – carborundum,
aloxite, alundum, etc.

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Applications of abrasives

Corundum : is a natural mineral which consists
of aluminium oxide. Hardest natural substance
after diamond.
 Used for shaping, finishing and polishing other tools.


Emery : natural abrasive consisting of
aluminium oxide and little amount of iron
oxide.
Silicon carbide : synthetic abrasive harder than
aluminium oxide.
 Used to grind metals like iron, brass and soft bronze.
 Used in non metals like wood and leather industries.
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
Zirconia aluminia : it is a mixture of
zirconium oxide and aluminium oxide.
 Used in casting and foundry industries.

Cubic boron nitride : is made up of
boron nitride with a cubic crystalline
structure.
 Used for hard coating material.

Diamond :
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Bonding materials

These are adhesives which holds the
abrasive grains together.
 Vitrified process :
 Silicate process :
 Elastic process :
 Rubber or vulcanite process :
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Grinding machines
 Grinding
machine is a power operated
machine tool where, the work piece is fed
against constantly rotating abrasive wheel
to remove thin layer of material from
work.
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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.

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Classification of grinding
machine
Bench grinding machine
 Surface grinding machine
 Cylindrical grinding machine
 Center less grinding machine
 Internal grinding machine
 Special purpose grinding machine

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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.
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Internal pump and piping arrangement for
coolant.
 Protective guard for safety.

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



Base
Column
Table traverse
and vertical feed
hand wheel.
Wheel guard
and protective
guard.
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
Working
 Work piece is clamped to the table by
operating magnetic chuck.
 Required grade of grinding tool is fixed to
spindle.
 Grinding operation is carried out be
operating both table traverse wheel and
vertical feed hand wheel.
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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.

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Working principle
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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.

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Cutting terminology
Speed : it is the peripheral speed of the
work piece per unit time. (m/min)
 Feed : it is the distance travelled by the
tool during each revolution of the work
piece. (mm/revolution).
 Depth of cut : it is the perpendicular
distance measured from the original
surface to the machined surface of the
work piece. (mm)


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