[One of Many]

If you have a feedrate overide knob, it gives you the control to increase or decrease based on conditions at present. I have my CAM defaults set to 5ipm on steel, 10ipm on aluminum and use the feedrate overide 10-150%.

I have always used the calculation of:

IPM Feed rate=(chip load per flute)*(number of flutes)*(spindle RPM)

You can look up the SFM rating of the material being cut as a guide to find the RPM values based on the cutter diameter, but IMHO, use it as a guide conservatively. The strength in the cutter influences this to a greater degree than relative load assumptions in the next step to calculate a feed rate. Keep in mind that this is the MAX feed rate. Actual feed rate may be between 0 and reality to sound and feel as it is in any manual operation.


A typical standard length cutter is (more or less) designed to take a full length cut at .002-.004 per flute on 1/4 of its circumference. See attachment for detail. Cutting a path using 1/2 of the circumference is twice the load it should handle at the same feed rate or depth of cut. From my experience the depth of cut needs to be about 1/3 the diameter in that usage. Lowering the feed rate only increases the chances for chatter.

Even so, you cannot trust a 3/16" cutter to produce a 3/16" slot. Do not count on success if a no slop fit is required. Most cutters will cut oversize between wander and spinning off center.

DC