When grinding inner holes, if the diameter of the grinding wheel is too large, the contact arc between the grinding wheel and the workpiece will increase, which will increase grinding heat and make cooling and arrangement difficult. If the diameter of the grinding wheel is too small, it is difficult to achieve the ideal grinding speed (30 meters/second~50 meters/second), resulting in an increase in grinding thickness, an increase in the overlap of the grinding particles, easy blunting of grinding, increased surface roughness of the inner hole, and reduced production efficiency. Therefore, in order to achieve good grinding results, the ratio of grinding wheel diameter to inner hole diameter should be appropriately maintained, generally between 0.5 and 0.9.