When machining shaft parts with lathe, in order to ensure coaxiality, it is necessary to drill central holes at both ends of the shaft. When turning, the two ends of the shaft are supported by the center, and then the excircle is turned. In this way, no matter how to turn around, the coaxiality of the shaft can be guaranteed. In addition, you can also clamp a piece of material on the chuck, lathe a cone pit, lathe a little excircle at both ends of the shaft, and punch a central hole. When the car is processed, one end is in the cone hole coming out of the car, and the other end is supported by the tailstock tip. This can also ensure the coaxiality of the turning shaft.