Question 1

When is effective diameter correction most important?

Accepted Answer

It is critical when ap/D < 0.25 (axial depth less than 25% of tool diameter), which is common in 3D finishing operations. At ap = 5% of D, the effective diameter is only 43% of nominal — running at nominal RPM would give less than half the intended cutting speed. The correction is less important for roughing operations where axial depth approaches the tool radius.

Question 2

Does the effective diameter affect feed per tooth calculation?

Accepted Answer

Yes. The chip load at the effective cutting point differs from the programmed feed per tooth because the engagement arc is different. For very shallow depths, the actual chip thickness is thinner than fz (chip thinning effect). Some machinists adjust both RPM and feed using the effective diameter. CAM systems like Mastercam and Siemens NX can automatically apply effective diameter compensation.