Discussion item selection policy to accommodate the space of the bearing ● When designing the shaft, because the rigidity and strength of the shaft are important, the shaft diameter, which is the inner diameter of the bearing, is initially determined. ● Figure 1.2 shows the approximate model and size of the main precision rolling bearings used on machine tools. The direction and size of the load● According to the size of the radial load and the axial load, the direction of the load (single direction or two directions), and the nature (vibration and shock), select the most suitable model. Generally speaking, the load capacity of roller bearings is greater than that of ball bearings. Rotation speed ● Select the bearing model according to the maximum rotation speed requirement on the assembly machine specification. ● The limiting speed of the bearing is greatly affected by the size of the load, the lubrication method, the accuracy of the bearing, the material of the cage, the shape of the cage, etc. It is necessary to conduct sufficient research. ● Generally, angular contact ball bearings and cylindrical roller bearings with less temperature rise are used for high-speed rotation. Rigidity ● To increase the rigidity of the rotating shaft, not only the rigidity of the shaft, the seat cover, but also the rigidity of the bearing should be important. ● Generally speaking, roller bearings are more rigid than ball bearings. ● Assembled angular contact ball bearings can increase rigidity through preload. Mounting and dismounting ● Selecting a separate type of bearing can improve the operability when mounting and dismounting the bearing during periodic inspections.