THE DIAMETRAL PITCH SYSTEM
One of the first steps in addressing to select gears is to determine what size spur gears are needed for a particular application. At all standard stock on market spur gears are made according to the diametral pitch system, a sizing system we will get to shortly. But before we do, it is helpful to know the meaning of several terms that are commonly used in the gear industry.
Diametral Pitch: the ratio of the number of teeth to the pitch diameter. (See Figure 2.2, 2.2B)
Pitch Circle: the imaginary circle that comes in contact with the imaginary circle of another gear when the two are in mesh. (See Figure 2.2A)
Pitch Diameter: the diameter of the pitch circle (See Figure 2.2B)
Tooth dimensions are important because they provide valuable information when quoting customer gearing.
