Tooth count divided by pitch diameter in inches, the tooth-size standard for inch gearing. A 20-tooth, 10 DP gear has a 2 in pitch diameter, and going from 10 to 20 DP halves the tooth size. Coarse industrial gears run around 2 to 8 DP and instrument gears 48 DP and finer. Helical gears are specified by normal or transverse DP, and the two must not be mixed up.
Gear's 8 diametral pitch, 14 and a half degree, old machine, so pull the cutter from the 14.5 set, not the 20 degree drawer.
Also heard as
- DP
- P
- pitch
Do not mix it up with
- Module: Module is the metric measure, and it works the other way: bigger module means bigger teeth.
Related terms
Module
The metric measure of gear tooth size: pitch diameter in millimeters divided by the number of teeth.
Circular pitch
The arc distance from one tooth to the same point on the next tooth, measured along the pitch circle.
Pitch diameter
The diameter of the pitch circle, the imaginary rolling circle on which tooth size and gear ratio are based.
Pressure angle
The angle between the line of tooth contact force and the tangent to the pitch circle, usually 20 degrees.