Bearing is in the process of mechanical transmission in the fixed part of the coefficient of friction and reduce the load. Can also be said that, while other parts which move relative to each other when in the bearing, used to reduce the friction coefficient of power delivery and maintain a fixed axis center position of a few. Bearings are an important part of modern mechanical equipment. Its main function is to support the mechanical rotation, to reduce the mechanical load of equipment in the course of transmission coefficient of friction. According to sport nature of the original friction, bearing can be divided into two types of rolling bearings and sliding bearings.