Depending on the bearing preload, the rigidity or rotational precision of the bearing arrangement can be improved. For example, the machine tool spindle bearing of the CNC lathe, the transmission gear bearing in the transmission shaft, the small motor bearing, or the bearing equipment for linear motion, etc. In some applications, if the bearing does not or only bears a small load and operates at high speed, preloading should be carried out on the bearing arrangement. In such a case, the function of preload is to give the bearing the least load, so as to avoid the damage of the bearing caused by the rolling of the rolling body. The preload can be radial or axial according to different bearing types. For example, cylindrical roller bearings, because of their design, only increase the preload in the radial direction, while thrust ball bearings and cylindrical roller bearing thrust bearings only increase the preload in the axial direction. Angular contact ball bearings and tapered roller bearings generally bear axial preload and are usually matched with another bearing of the same type in a back-to-back or zero-distance method. And deep groove ball bearings usually apply axial preload in the same way. In order to better achieve the purpose of preloading, a radial internal structural clearance that exceeds the general group should be adopted, so that it can be made as an angular contact ball bearing. Surface tension above zero. The torque is accurate, in order to turn stable!