Tc 9-524 fundamentals of machine tools

Selection of Grinding Wheels and Speeds
The grinding wheel speed is changed by using various sizes
of pulleys on the motor and spindle shafts. An instruction
plate on the grinder gives both the diameter of the pulleys
required to obtain a given speed and the maximum safe speed
for grinding wheels of various diameters. Grinding wheels are
safe for operation at a speed just below the highest
recommended speed. A higher than recommended speed may
cause the wheel to disintegrate. For this reason, wheel guards
are furnished with the tool post grinder to protect against
injury. Always check the pulley combinations given on the
instruction plate of the grinder when you mount a wheel. Be
sure that the combination is not reversed, because this may
cause the wheel to run at a speed far in excess of that
recommended. During all grinding operations, wear goggles
to protect your eyes from flying abrasive material.
Dressing the Grinding Wheel
The grinding wheel must be dressed and trued. Use a
diamond wheel dresser to dress and true the wheel. The
dresser is held in a holder that is clamped to the drive plate.
Set the point of the diamond at center height and at a 10° to
15° angle in the direction of the grinding wheel rotation. The
10° to 15° angle prevents the diamond from gouging the
wheel. Lock the lathe spindle by placing the spindle speed
control lever in the low RPM position.
NOTE: 
The lathe spindle does not revolve when you are
dressing the grinding wheel.
Remove the diamond dresser holder as soon as the dressing
operation is completed. Bring the grinding wheel in contact
with the diamond by carefully feeding the cross slide by hand.
Move the wheel clear of the diamond and make a cut by
means of the cross slide. The maximum depth of cut is 0.002
inch. Move the wheel slowly by hand back and forth over the
point of the diamond. Move the carriage if the face of the
wheel is parallel to the way of the lathe. Move the compound
rest if the face of the wheel is at an angle. Make the final
depth of cut of 0.0005 inch with a slow, even feed to obtain a
good wheel finish.
Before you begin the grinding operation, cover the ways
with a heavy piece of paper or use a shallow pan of water
placed on the ways to collect the grinding dust that will
accumulate from the grinding. This is to ensure none of the
grinding burns to the ways or gets under the carriage which
will cause the lathe premature wear. If you use a piece of
paper, pay close attention that the sparks from the grinding
operation do not cause the paper to ignite. If you use a
shallow pan of water, make sure water is not spilled on the
ways of the lathe. After all grinding operations, thoroughly
clean and oil the lathe to remove any grinding dust that the
paper pan of water missed.