The shaft is supported by a bearing, and the shaft section matched with the bearing is called a journal. The journal is the assembly benchmark of the shaft, and its accuracy and surface quality are generally higher. Its technical requirements are generally formulated according to the main functions and working conditions of the shaft: the surface roughness is generally ra2.5 ~ 0.63 of the shaft diameter matched with the transmission parts μ m. The surface roughness of the supporting shaft diameter matched with the bearing is Ra0.63 ~ 0.16 μ m。