| 摘要 |
PURPOSE:To obtain a minute metallic crystal grain of a drill part, to prevent a crack, and to improve the strength and the rigidity of a cutting edge, by suppressing a burr from being protruded by executing a non-slip control so that an excess metallic material is not protruded freely from a forming recessed part. CONSTITUTION:When a stock 1 is supplied between a pair of forming dies 3 of a punching device, the tip part of a shaft part 2 is inserted and held between forming recessed parts 4 of the dies 3 and a drill part 5 is formed, an excess metallic material protruded from the forming recessed parts 4 goes in between opposed tapered surfaces 9, and a burr 6 is formed. In this case, the excess metallic material protruded from the recessed parts 4 is detained to a slender recessed groove 23 being a non-slip means A and its slip is stopped, and it is not forged in a free state, therefore, a tensile distortion is not generated, a metallic crystal particle of the drill part 5 becomes minute, and also, no crack is generated. The stock 1 being in a state that the burr 6 has been formed is fed between a pair of dies, a thread is cut by a thread cutting part, and immediately before the thread cutting is ended, the burr 6 is cut down by the deburring surface. |
