Quenched steel must be finished after heat treatment to ensure the dimensions and surface roughness required by the drawings. However, the quenched steel after heat treatment is difficult to machine due to its high hardness. Some workpieces require intermittent cutting or high surface accuracy. The grinding method was often used to improve the quality of hardened steel. Workpiece accuracy, the following briefly describes the machining process of several hardened steel. Gear processing technology: blanking - forging - normalizing - roughing - heat treatment (quenching + high temperature tempering) - finishing car - tooth surface grinding - inspection storage. Ball screw processing technology: blanking - forging - annealing - cutting - heat treatment - grinding - inspection and storage. Automotive axle machining process: blanking - forging - normalizing - turning - pull spline - heat treatment - grinding. From the processing point of view, the above several quenched steel parts need to be grinding to ensure the size and roughness requirements of the drawings, the gear is due to intermittent cutting, turning tools can not be processed; and the ball screw and the car axle belongs High surface precision, using grinding to achieve surface finish.