When processing the piston rod, the middle part of the rod needs to be nitrided. For example, the hardness of the middle part of the rod before nitriding is 210-220HV, and the hardness after nitriding is 400-410HV, which increases exponentially. After nitriding the piston rod, there will be a 0.15mm margin in the middle part of the rod. The middle part of the piston rod needs to be processed to a diameter of 22.15 (+0, -0.03). When using grinding processing, it takes about 60 minutes to process one piece, and the lower production efficiency cannot meet the current batch production. At present, most efficient turning processes are used. However, during turning, due to the increased hardness of the piston rod, the blade is prone to chipping and yielding when turning the rod. Once yielding occurs, the size cannot be guaranteed, and blade damage increases the direct economic cost of purchasing the tool.