The lead screw is mainly used for turning threads at a fixed distance, and the feed of the cart is relatively large. The function of the screw is to make the servo drive. The function of the designed screw is that the spindle rotates once, and the tool rest can move the corresponding distance accurately to ensure the pitch of the lathe is equal, so the screw is used to turn threads.

When the polished rod is used in the common excircle, the feed is much smaller than that of the lead screw, and stepless speed regulation can be realized. The polished rod cannot guarantee the accurate transmission ratio from the structure. Therefore, it is generally used for turning excircles, end faces and inner holes. Generally, there is no need to turn the thread;

From the efficacy of the two, we know that we can't use only one screw to replace the polished rod and the screw at the same time.