Module System Gear Design

Gear Design Based upon Module System. The module of a gear is equal to the pitch diameter divided by the number of teeth, whereas diametral pitch is equal to the number of teeth divided by the pitch diameter. The module system (see accompanying table and diagram) is in general use in countries that have adopted the metric system; hence, the term module is usually understood to mean the pitch diameter in millimeters divided by the number of teeth. The module system, however, may also be based on inch measurements and then it is known as the English module to avoid confusion with the metric module. Module is an actual dimension, whereas diametral pitch is only a ratio. Thus, if the pitch diameter of a gear is 50 millimeters and the number of teeth 25, the module is 2, which means that there are 2 millimeters of pitch diameter for each tooth. The table Tooth Dimensions Based Upon Module System shows the relation among module, diametral pitch, and circular pitch.

German Standard Tooth Form