Bearing is a kind of important modern machinery and equipment parts. Its main function is to support the mechanical rotator, reduce the coefficient of friction in the process of the movement, and guarantee its rotation accuracy.

By the frictional properties of motion elements, bearing can be divided into two categories, the rolling bearing and sliding bearing. The rolling bearing is standardization, seriation, but compared with sliding bearing radial size of it, the vibration and noise is bigger, the price is higher also. 

Rolling bearings generally consists of outer ring, inner ring, rolling body and keep the frame of four parts. According to the shape of the roller, the rolling bearing can be divided into two types: ball bearings and roller bearings.