MULTI-PITCH SCREW, AND METHOD AND DEVICE FOR MANUFACTURING MULTI-PITCH SCREW

摘要

[PROBLEMS] To provide a method for manufacturing a multi-pitch screw with specified threads and pitches by rolling. [MEANS FOR SOLVING PROBLEMS] The route of a general (equal lead angle) spiral screw is formed of the equal pitch projections (610) and (620) of existing rotating dies (61) and (62), and the stepwise route of the screw formed of the stepwise projection (632) of the rotating die (63) with a non-equal lead angle is overlapped with the route of the general spiral screw to efficiently roll multi-pitch threads. Since only one non-equal lead angle rotating die (63) is used, the threads are not smoothened out by stepwise projections of the plurality of rotating dies with the non-equal lead angle.