Ball screw: the ball screw can convert rotary motion into linear motion, or it is an ideal product to convert linear motion into rotary motion. the ball screw consists of a screw, a nut and a ball. Its function is to convert rotary motion into linear motion, which is the further extension and development of the ball screw. Ball screw pairs are widely used in various industrial equipment and precision instruments due to their low friction resistance. It can realize high-precision linear motion under high load. however, due to the fact that spruce screw does not have the self-locking capacity of trapezoidal screw, attention should be paid in the use process.