Modulus is a factor that determines the size of the teeth. The gear module is defined as a basic parameter of the modular gear tooth, which is artificially abstracted to measure the number of gear teeth. The goal is to standardize gear cutting tools and reduce costs. The modulus of the straight, helical and conical gears can be referenced to the standard modulo series.

With the continuous improvement of the level of industrial development, many custom-made mass-produced gears use non-standard moduli, making its significance weak.

If the gear has a certain number of teeth, the larger the module, the larger the radial dimension of the wheel. Modular series standards are based on design, manufacturing and inspection requirements. For gears with non-straight teeth, the modulus has the difference between the normal modulus mn, the face surface modulus ms, and the axial modulus mx. They are all at their own pitch (normal pitch, face pitch, and axis The ratio between the pitch and the pi is also in millimeters. For bevel gears, the module has a large end modulus me, an average modulus mm, and a small end modulus m1. For the tool, there is a corresponding tool module mo. The standard modulus is widely used. In metric gear drives, worm drives, synchronous toothed belt drives and ratchets, gear couplings, splines, etc., the standard module is a basic parameter. It plays the role of basic parameters for the design, manufacture and maintenance of the above parts.

Modulus m = pitch circle diameter d / number of teeth z = pitch p / pi

It can be seen from the above formula that the basic parameters of the gear are the diameter of the circle and the number of teeth. The modulus is only a parameter set by man and it is a ratio. It is related to the tooth thickness of the subcirculation, so it can measure the size of the teeth and is a historical product of the industrialization process. .