What is a circular pitch ?
A circular pitch is the distance between the corresponding points of the adjacent teeth measured on the pitch circle. In other words, it is the space between the teeth.
In order for the gears to mesh properly, the meshing gear teeth must be of an equal size. That is to say, the circular pitches must be equal.
If d is the pitch diameter and z is the number of teeth, its circular pitch p can be obtained by the formula :
p = π d / z
That is, the circular pitch is calculated by dividing the pitch circle circumference by the number of teeth.
Because the above formula for the circular pitch contains the circular constant π, the calculation becomes cumbersome.
For that reason, in general, π in the fornula is eliminated (by dividing the right side by π) to obtain a clean numerical value of module m which is widely used.
In short, m = d /z becomes the formula for the module.
The diagram below shows the circular pitch graphically.
相关链接 - 节距