#### Tapping Formulas Tapmatic Corporation

Tapping Formulas. RPM = (SFM x ) divided by D. D = Diameter of Tap in inches. SFM = ( x D x RPM) divided by 12. D = Diameter of Tap in inches. Inch Taps. Drill Size = Major Diameter of Tap minus. .01299 x % of Full Thread. # Of Threads / inch.