Pitch diameter - in imperial units (gears)
A gear or cogwheel is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part to transmit torque, in most cases with teeth on the one gear being of identical shape, and often also with that shape on the other gear.
Pitch is the distance between a point on one tooth and the corresponding point on an adjacent tooth.
Is a predefined diametral position on the gear, where the circular tooth thickness, pressure angle and helix angles are defined. The standard pitch diameter is a basic dimension and cannot be measured, but is a location where other measurements are made. Its value is based on the number of teeth, the normal module (or normal diametral pitch), and the helix angle.
|d||Pitch diameter (in)|
|N||Number of teeth (dimensionless)|
|Pd||Diametral pitch (1/in)|
|ψ||Helix angle (degree)|