Bearingis an important component in contemporary machinery and equipment. Its main function is to support the mechanical rotating body, reduce the friction coefficient during its movement, and ensure its turning accuracy.

According to the different friction properties of moving elements, bearings can be divided into two categories: roller bearings and plain bearings. Roller bearings have been standardized and serialized, but compared with sliding bearings, its radial size, vibration and noise are larger, and the price is higher.

Roller bearings are generally composed of four parts: outer ring, inner ring, rolling body and cage. According to the shape of roller elements, roller bearings are divided into two categories: ball bearings and roller bearings.