부산대학교 도서관

To present a method of manufacturing a multipitch screw easily by using flat dies suited to mass production. A flat die 4 includes linear ordinary screw threads 40a, and multipitch screw threads 40b consecutive to the ordinary screw threads 40a, slightly shorter in height than the ordinary screw threads 40a, with both side walls formed alternately and consecutively, alternating between a section departing from the central line 40c of screw threads and an approaching section along a central line 40c, and symmetrically to the central line 40c of screw threads. After forming the tacks of a constant lead angle screw on the outer circumference of a shaft-like blank piece by the ordinary screw threads 40a, tracks of a multipitch screw are formed by the multipitch screw threads 40b, and therefore the tracks of a multipitch screw varying in the force applied at the time of rolling can be formed easily.