Get spindle speed and Z feed rate for cutting a thread with a thread mill helical interpolation pass, instead of tapping.
RPM = (SFM x 3.82) / tool diameter. Pitch = 1 / TPI. Z feed = RPM x pitch, since one full helical lap advances the tool exactly one thread pitch.
How it works
A thread mill cuts the full thread profile while helically interpolating around the bore or boss, advancing one pitch per full circle just like a tap, but running at milling surface speeds since the tool has real relief and a true cutting edge rather than a forming chisel point.
FAQ
Why thread mill instead of tap? Thread milling avoids tap breakage in blind or hard holes, handles multiple thread sizes with one tool by adjusting the helical radius, and generally produces a better finish in tough materials.
Related Guides
CNC Calculators · Helical Interpolation Calculator · Tapping Speed Calculator