Bearing ("Bearing", Japanese called "axis by") is in the process of mechanical drive from the fixed and reduce the load of the components of the friction coefficient. It can be said, When other mechanical relative movement to each other on the shaft, is used to reduce the coefficient of friction in the power transmission process and maintain the fixed parts of the shaft center position. The bearing is an important contemporary machinery and equipment parts. Its main function is to support the mechanical rotating body, for reducing the coefficient of friction of the mechanical load of equipment in the transmission process. By friction the different nature of the moving element, the bearing may be divided into two types of rolling bearings and sliding bearings.