Bearing is an important part of modern mechanical equipment. Its main function is to support the mechanical rotating body, reduce the friction coefficient during its movement and ensure its rotation accuracy.

According to the different friction properties of moving elements, bearings can be divided into rolling bearings and sliding bearings. Among them, rolling bearing has been standardized and serialized, but compared with sliding bearing, its radial size, vibration and noise are larger and its price is higher.

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