We can divide the existing lathe centers into two types, namely, the front center and the rear center. Both of them can be used for centering and bear the gravity and cutting force of the workpiece. However, as lathe centers, there are great differences in function and use between the two. Next, I will introduce them in detail.

1. Front top tip: Generally speaking, the front top tip can be directly installed in the taper hole of the lathe spindle, and can rotate with the workpiece without relative movement, so it is not necessary to quench in use. Sometimes, the lathe can also clamp a self-made steel front tip with a 60 ° cone angle with a three jaw self centering chuck. In addition, in order to prevent the displacement of the center due to the action of axial force during turning, the clamping part of the chuck on the self-made center should be made into a bench type. If the lathe is used again after the center is removed from the chuck, it must re turn the 60 ° cone.

2. Rear center: the rear center can be divided into two types, namely, the fixed center and the rotary center. The fixed center has the advantages of good cutting performance and accurate centering, but there is sliding friction between the center hole and the hard tip, which is easy to wear and burn the center. The movable center is equipped with a rolling bearing. The center will rotate with the workpiece and can work normally at high speed. However, the rigidity of the movable center is poor, and sometimes it will jump and reduce the machining accuracy. Therefore, the movable center is only applicable to the workpiece with low precision requirements.

However, both the front top and the rear top need the cooperation of Morse taper. The principle of friction is used. The pulling out is pushed out by jackscrew and the principle of lever is used.