Bearing is an important part of contemporary machinery and 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 the moving elements, bearings can be divided into rolling bearings and sliding bearings. Among them, the rolling bearing has been standardized and serialized, but compared with the sliding bearing, its radial size, vibration and noise are larger, and the price is also higher.

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