Tc 9-524 fundamentals of machine tools

TT = (WW X FF X WRPM) + 12
Where TT = Table travel in feet per minute
WW
= Width of wheel
FF
= Fraction of finish
WRPM
= Revolutions per minute of workpiece
12
= Constant (inches per foot)
The fraction of finish for annealed steels is 1/2 for rough
grinding and 1/6 for finishing; for hardened steels, the rate is
1/4 for rough grinding and 1/8 for finishing.
For example, a l-inch-wide wheel is used to rough grind a
hardened steel cylinder with a work RPM of 300.
Table travel =
(1 x 1/4 x 300)
÷ 
12 = (75) 
÷ 
12 = 6.25 FPM
After the calculations have been completed, set the machine
for the proper traverse rate, turn on the table traverse power
feed, and grind the workpiece.
Check the workpiece size often during cutting with
micrometer calipers. Check the tailstock center often and
readjust if expansion in the workpiece has caused excessive
pressure against the drilled center in the workpiece.
The finishing cut should be slight, never greater than 0.001
inch, and taken with a fine feed and a fine grain wheel.
If two or more grinding wheels of different grain size are
used during the grinding procedure, each wheel should be
dressed and trued as soon as it is mounted in the grinding
machine.
Conical Grinding
Most conical grinding is performed in the same manner as
plain cylindrical grinding. Once the grinding machine is set
up, the table is swiveled until the correct taper per inch is
obtained. Steep conical tapers are normally ground by
swiveling the headstock to the angle of taper. Whichever
method is used, the axis of the grinding wheel must be
exactly at center height with the axis of the work.
5-21

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