Understanding The How and Why of Choosing the Right Pitch

There are three designators of pitch within gearing: gears can be produced to diametral pitch (DP), circular pitch (CP), or module, also known as metric pitch. The most commonly used designation of pitch in the United States is diametral pitch. This method of determining the size of the gear tooth is based on the unit circle. If you draw a circle that is one inch in diameter and equally space 16 teeth around this circle wherein the pitch diameter is overlaying the one-inch circle, then you have created a 16DP gear tooth form. If you continued to draw the same size teeth on a two-inch circle, then you would have 32 teeth, and the pitch would be 32/2, or 16DP.