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CNC is producing a taper in my tapped hole


Apr 16, 2015
the .030 is the feed GIBBS CAM gave.... I installed the info as 40 TPI.... and the rpm is 400.... the program figures the feed..... based on the rpm
tapped 100 of thousands of holes with the same program.... I changed the lead on the tap to .170 in the description of the tap in GIBBS, but it didnt make a different

Gibbscam allows you to enter a "Tap %" modifier below the RPM on your tapping process. The field is greyed out when set to "Rigid Tap" but available when set to "Tap". I got burned by this once (it was set at 75%), I later learned it could be used for those floating tension / compression heads to keep pressure on the tap. If you accidentally set this field to 120% that would explain the .03" pitch on a 4-40.

From the Gibbs mill manual:

The value entered here specifies the percentage of the feedrate that will be used on the tapping
cycle. This text box appears only if Tap is the selected Entry/Exit Cycle.
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