Rolling bearings developed on the basis of sliding bearings, its working principle is to replace sliding friction by rolling friction, generally consists of two rings, a group of rolling body and a holder composed of a strong universality, standardization, high degree of serialization of mechanical base parts.Due to different working conditions of various machines, different requirements are put forward for rolling bearings in terms of load capacity, structure and service performance.For this reason, rolling bearings need a variety of structures.However, the most basic structure is composed of an inner ring, an outer ring, a rolling body and a cage.

For centripetal SKF bearing, the inner ring is usually tightly matched with the shaft and operates together with the shaft, and the outer ring is usually transitional matched with the bearing seat or the mechanical shell hole to play a supporting role.However, in some cases, there are also outer ring operation, the inner ring is fixed to play a supporting role or the inner ring, the outer ring are running at the same time.For thrust bearings, the shaft ring that is tightly matched with the shaft and moves together is called the seat ring that is transitively matched with the bearing seat or the mechanical shell hole and plays a supporting role.The rolling body (steel ball, roller or needle) in the bearing is usually evenly arranged between the two rings with the help of the cage for rolling movement, its shape, size and number directly affect the bearing's load capacity and performance.The cage can not only separate the rolling body evenly, but also guide the rolling body to rotate and improve the internal lubrication performance of the bearing.

Compared with sliding bearings, rolling bearings have their own advantages and disadvantages, and each has a certain number of application occasions. Therefore, they can not completely replace each other, and they develop in a certain direction and expand their own fields.However, because of the outstanding advantages of rolling bearings, there is a tendency of latecomers.Rolling bearing has become the main supporting type of machinery and is used more and more widely

When rolling bearings are working, sliding friction causes bearing heating and wear. Especially under high temperature operation conditions, the effect of inertial centrifugal force aggravates friction, wear and heat. If it is serious, it will cause cage burns or fracture, so that the bearing can not work normally.Therefore, in addition to a certain strength, the material of the cage must have good thermal conductivity, small friction coefficient, good wear resistance, strong impact toughness, small density and linear expansion coefficient close to the rolling body.In addition, the stamping cage needs to undergo more complex stamping deformation, but also requires that the material has good machining performance.Some of the most demanding cages are coated with silver.