The LEBUS double fold winding system is widely used in winch drum device of multilayer winding of the steel wire rope, and the step retaining ring at both ends of the drum is the key part of the traditional rope arranging mechanism. This kind of step retaining ring can be used to realize the automatic reversing and winding of the steel wire rope，and the problems such as shortening the service life of the steel wire rope and disordered rope arrangement caused by severe extrusion and wear can be avoided when the steel wire rope transits from the lower layer to the upper layer. In view of the difficulty processing of the step retaining ring，CNC remanufacturing for an old C6031A horizontal lathe was carried out, including the remanufacturing of the main motion, the remanufacturing of the guide rail, the remanufacturing of the feed motion and the design of the special CNC system. The results show that the remanufactured C6031A CNC lathe can completely meet the requirements of turning various step retaining rings of the winch drum, with remarkable economic and social benefits.