To provide a form-rolling die with which a male screw and a deep groove are formed without deforming the thread of the the male screw in one process and consequently the screw thread with the deep groove is manufactured at a low cost.
This form-rolling die consists of the combination of a fixed die 12 and a moving die 13 and a projected line 14 for forming the deep groove having steep angle is provided in arrangement of a certain interval and over the entire area respectively on the opposed form-rolling faces of the fixed die 12 and the moving die 13. By successively setting this form-rolling face in the temporary forming part A of the male screw, a deep groove forming part B, the main forming part C of the male screw and the finish forming part D of the male screw toward the rear end from the tip of the inlet side and forming a recessed groove between the deep grooves with a projected line 15 provide in the temporary forming part A of the male screw to the shaft part of a rivet, the biting of the projected line 16 in the main forming part C of the next male screw starts from the recessed groove, so that the occurrence of resistance and impact in the biting of the projected line 16 of the main forming part C is prevented and the shaft part of the rivet is smoothly form-rolled.
Higashio Masahiro
Torii Kazuhisa