Get spindle speed and feed rate for rigid tapping from tap diameter, threads per inch, and target surface speed.
RPM = (SFM x 3.82) / D. Pitch = 1 / TPI. Feed rate = RPM x pitch, since a rigid tap must advance exactly one pitch per revolution.
How it works
Rigid tapping locks the spindle rotation to the Z feed so the tap advances at exactly the thread pitch per revolution. Taps also run noticeably slower surface speeds than drills or end mills since the full flank of the thread is forming or cutting at once.
FAQ
What if my feed and RPM do not match the pitch? On a rigid tapping cycle the control should compute feed from RPM and pitch automatically. If you are setting both manually, a mismatch will strip the thread or snap the tap.
Related Guides
CNC Calculators · Tap Drill Size Calculator · Thread Calculator