Internal Diameter
The diameter of a circle coinciding with the tops of the teeth of an internal gear. Usually referred to as ID or minor diameter.
Whereas: From Gear Data z = number of teeth in gear (61) Mn = normal module pitch (8) DPn = normal diametral pitch (3.175)
Formula: Internal Diameter - Module Pitch: = (z-2)*Mn = (61-2)*8 = 59*8 = 472mm Internal Diameter - Diametral Pitch: = (z-2)/ DPn = (61-2)/3.175 = 59/3.175 = 18.582inches