Ball screw assembly is consisted of screw, nut and balls. It is to transfer the rotary motion into linear motion or transfer the linear motion into rotary motion. Ball screw is widely used for all kinds of industrial equipments and precision instruments. Especially in recent years, it is widely used in CNC machine tools. Yigong ball screw is made by grinding and whirling, not rolled, and it has two kinds of ball screw P for positioning and T for transmission,