Research Project Selection Policy Space for Bearings ● When designing a shaft, the shaft diameter, that is, the bearing inner diameter, was initially determined because the rigidity and strength of the shaft were considered important. ● Figure 1.2 shows an overview of the types and sizes of the main NACHI precision rolling bearings used in machine tools. Direction of load ● Select the most suitable model according to the magnitude of radial load and axial load, direction of load (single direction or two directions), and nature (vibration and shock). Generally speaking, the load capacity of roller bearings is larger than that of ball bearings. Rotational speed ● Select the bearing type according to the maximum rotation speed requirement on the assembled machine specification. ● The limit speed of the bearing is greatly affected by the magnitude 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, for high-speed rotation, use angular contact ball bearings and cylindrical roller bearings with less temperature rise. Rigidity ● In order to increase the rigidity of the rotating shaft, it is important not only to pay attention to the rigidity of the shaft, but also to the rigidity of the housing and the bearing. ● Generally speaking, the rigidity of roller bearings is higher than that of ball bearings. ● Modular angular contact ball bearings can be preloaded to improve rigidity. Mounting and dismounting ● Selecting the separable bearing can improve the operability when mounting and dismounting the bearing during periodic inspection.