involute spline

Diametral pitch and Module

This applies to DIN 5480, DIN 5482, ISO 4156, ANSI B92.2M, ANSI B92.1, and similar splines

The imperial system uses DIAMETRAL PITCH to characterize teeth size. Diametral pitch is always in inches.

Pd = N/D = number of teeth to inches of pitch diameter

N: number of teeth

D: pitch diameter in inches

The metric system uses MODULE to characterize teeth size. Module pitch is always in millimeters.

Module m = D/N = mm of pitch diameter per tooth

N : number of teeth

D : pitch diameter in mm

A gear with 10 teeth and 1.000 inch pitch diameter

10 diametral pitch = 10 / 1.000in

The same gear in metric:

2.54 module = 25.4mm / 10

m = 25.4/Pd Pd = 25.4/m