| 摘要 |
PROBLEM TO BE SOLVED: To provide the structure of dies with which a screw is easily manufactured from a screw base stock having a circular cross section by roll forming regardless of the size of the screw. SOLUTION: In the structure of a pair of dies for rolling non-circular tapping screws by using the screw base stock having the circular cross section, on a die on one side, a screw thread forming part having a specified depth for forming the screw thread of the non-circular tapping screw is provided at a specified pitch angle and, on a die on the other side, a screw thread forming part for forming the screw thread of the non-circular tapping screw is provided at a specified pitch angle and shallower than that of the die on the one side. Furthermore, on the die on the other side, groove parts which are formed into the depth deeper than that of the the screw thread forming part of the die on the one side are periodically provided at least in a different direction from the axial direction of the rolled screw base stock. COPYRIGHT: (C)2004,JPO
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