Handy Formulas

Formulas Based on 3/8-16 P. Thread

P.D. = Pitch Diameter
Depth of 16 P. Thread = .0406
Helix Angle: 3 deg. 24'
P.D. of 3/8-16 = .334
Cotan 3 deg. 24' = 16.832

Example information based on the following:

RPM Approx. 320
Die O.D.: 5.940
P.D. of die = 5.899
Cotan 7 deg. 0' = 8.1143
FPM = Feet Per Minute
IPM = Inches Per Minute
Speed-up die tilt angle: 7 deg. 0'
P.D. of die = O.D. of die minus one depth of thread

Rolling with Speed-up Dies:

Example 1:

To find FPM using RPM and tilt angle wanted:

P.D. of work x Pi / cotan of tilt angle x P.D. of die / P.D. of work x RPM = IPM / 12 = FPM

Example 2:

To find RPM using FPM and tilt angle wanted:

FPM x 12 / P.D. of die x P.D. of work x cotan of tilt angle / Pi / P.D. of work = RPM

Example 3:

To find tilt angle using RPM and IPM wanted:

RPM x P.D. of work x Pi x P.D. of die / P.D. of work / IPM = cotan of tilt angle

Rolling with Annular Ring Dies:

3/8 -16 annular thrufeed rolling

P.D. of work x Pi / cotan of tilt angle x P.D. of work / P.D. of work x RPM = IPM / 12 = FPM