Radial ball bearings and tapered roller bearings mostly use forgings. The reasons for using a large number of forgings are: (1) The ductility of the metal is used to form the required size and shape, which reduces the cutting allowance. In addition, it can apply high-speed processing machines such as punching machines and rolling machines, and the productivity is high. (2) If the shear processing surface of the bar, pipe, and plate and the bottom exhaust during processing are removed, the metal flow line of the product will not be cut off. In addition, the material strain makes the grains finer, and the work hardening improves Material strength, etc., can improve the performance of the material itself. In addition, large-diameter bearings used in wind turbines and industrial machinery must use forgings.