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• If the part has a uniform cross section through feed grinding can be used. Otherwise infeed grinding will have to be used. For infeed grinding the parts are placed between the wheels, ground, and then pulled out. Through feed grinding has the parts move in a steady flow between the wheel.

			infeed	parts
grinding				grinding				governing
wheel				wheel				wheel
				through
				feed

10.2.4 Internal

• Internal grinding is similar to other forms of rotational grinding, except that as the part rotates the internal features are ground by a smaller wheel.

part

grinding wheel

• Using a smaller wheel requires higher grinding speed which increases the challenge of this process.

10.3 GRINDING WHEELS

•The wheels are typically made with a bonded abrasive.

•common abrasives used are,

Aluminum oxide

Silicon carbide

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•Grain size is typically from 6 to 600.

•The bonding mechanisms used commonly are,

-vitrified

-resinoid

-rubber

-shellac

-silicate

•The Grade of the wheel is a measure of the ability to retain grit. If a wheel is Grade A it is soft, if it is Grade Z, it is very hard.

•The wheels are also given a structure number. 1 indicates a dense structure, whereas, 15 indicates an open structure.

•Loading of a wheel refers to the embedding of swarf in the voids.

•Glazing occurs when the grit has dulled, but is still bonded to the surface.

•Grinding wheels should undergo a dressing process.

•Many grinding wheels are shaped. This shaping is done while the wheel in the machine using diamond, or other hard shaping tools.

10.3.1 Operation Parameters

•The wheel can be made to act soft by increasing work speed, and decreasing wheel speed. The wheel can be made to act hard by reversing the parameters.

•Typical operation parameters are a depth per pass.

materials	Depth per pass (in)
softer plastics	0.005 to 0.0005
aluminum	0.003 to 0.001
ductile cast iron	0.003 to 0.001
mild steel	0.003 to 0.001
brass	0.003 to 0.0005
stainless steel	0.001 to 0.0005

• The wheel normally turns to give a CS of 3500 to 6000 fpm and wheels range from diameters of a few inches to a few feet.