1. lathe heat treatment of materials, heat treatment must leave room for 0.3 mm, taking note of car parts in the process of high temperature margin to stay. Because it has the thermal swelling factors. 2. the vehicle speed to lower the speed of hot material, ? 30 speed 360, ? 30~ ? 80 RPM 230, ? 80~ ? 200 RPM 130, ? 200~ ? 300 RPM 90. feed the amount 0.1 mm per turn.