The basic size parameter of metric gearing, equal to reference pitch diameter in millimeters divided by tooth count, so a 40-tooth, 2 module gear has an 80 mm pitch diameter. Larger module means bigger, stronger teeth. Standard tooth proportions follow from it: addendum is one module and whole depth about 2.25 module. Module equals 25.4 divided by diametral pitch.
It's a 3 module, 20 degree gear, so order the cutter by module, not by DP, or the teeth won't match.
Module and DP gears rarely mesh even when the sizes look close: 2.5 module works out to 10.16 DP, not 10.
Also heard as
- m
- metric module
Do not mix it up with
- Diametral pitch: Diametral pitch is the inch system and works backward: a larger DP number means smaller teeth.
Related terms
Diametral pitch
The inch measure of gear tooth size: number of teeth per inch of pitch diameter, larger number for finer teeth.
Pitch diameter
The diameter of the pitch circle, the imaginary rolling circle on which tooth size and gear ratio are based.
Circular pitch
The arc distance from one tooth to the same point on the next tooth, measured along the pitch circle.
Addendum
The radial height of a gear tooth above the pitch circle, normally one module for a standard tooth.