Bearings are an important part of contemporary machinery. 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 friction properties of moving components, bearings can be divided into two categories: rolling bearings and sliding bearings. Among them, the rolling bearing has been standardized and serialized, but its radial size, vibration and noise are larger and the price is higher than that of the sliding bearing.

Rolling bearings generally consist of an outer ring, an inner ring, a rolling element and a cage. According to the shape of the rolling element, the rolling bearing is divided into two categories: ball bearing and roller bearing.