| 摘要 |
In the present invention, die parts having rigid surfaces that are relatively displaced with respect to a thread material (B) whilst crimping the same are used to form roll a double-threaded body. The die parts are provided with: a precursor processing region including a region which is, in a virtual surface obtained by connecting the outermost surfaces of the die parts, gradually approached towards the axis center of the thread material and in the relative displacement direction, and a region which is gradually separated from the axis center; and a double-threaded-part forming region in which a plurality of recesses, which have an approximately parallelogram shape when viewed from the normal direction of the virtual surface and are recessed from the virtual surface, are provided in a plurality of rows in the relative displacement direction. Thus, when a double-threaded body is formed, rolling defects related to cylindrical thread materials are reduced, and the mass production of highly precise double-threaded bodies is possible |
