Machinery Repairman

very important because the cutter will be dulled or
even made useless by overheating. It is almost
impossible to provide any fixed rules that will govern
cutting speeds because of varying conditions from job
to job. Generally speaking, you should select a
cutting speed that will give the best compromise
between maximum production and longest life of the
cutter. In any particular operation, consider the
following factors to determine the proper cutting
speed:
Hardness of the material being cut: The harder
and tougher the metal being cut, the slower
should be the cutting speed.
Depth of cut and desired finish: The amount of
friction heat produced is directly proportional
to the amount of material being removed.
Figure 7-81.—Rack milling attachment.
Cutter material: You can operate high-speed
steel cutters from 50 to 100 percent faster than
carbon steel cutters because the high-speed
cutters have better heat-resistant properties.
Depending on the setup, you can operate
carbide cutters at up to 4 times the speed of
high-speed steel cutters.
Type of cutter teeth: Cutters that have
undercut teeth cut more freely than those that
have a radial face. Therefore, you may run
cutters with undercut teeth at higher speeds.
Sharpness of the cutter: You can run a sharp
cutter at a much higher speed than a dull cutter.
Therefore, you can often make finishing cuts at Use of coolant: Sufficient coolant will usually
a speeds 40 to 80 percent higher than that used cool the cutter so that it will not overheat even
in roughing. at relatively high speeds.
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