Tapping Formulas

RPM = (SFM x 3.82) divided by D

D = Diameter of Tap in inches

SFM = (3.14 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

Inch Taps % of Full Thread = Threads/in x

Major Dia. of Tap minus Drill Diameter .01299

Metric Taps Drill Size = Major Diameter of Tap (mm) minus

% of Thread x Metric Pitch 76.98

Metric Taps % of Full Thread =

76.980 Metric Pitch

x (Basic Major Diameter (mm) minus Drilled Hole (mm))

Form Tap Drill Size = Basic Tap OD

minus

.0068 x % of Threads Threads / Inch

Inch Taps IPM (For Threads) = RPM divided by TPI (Threads per Inch)

Inch Taps IPR (For Threads) = 1 divided by TPI

Inch Taps IPM (Inches Per Minute) = IPR x RPM

Inch Taps IPR (Inches Per Rev.) = IPM divided by RPM

Metric Taps MM/Min = RPM x Metric Pitch

Inch Taps In/Min = RPM divided by # of Threads / in.

Distance = Rate x Time

Time =

Distance Rate