| 摘要 |
PURPOSE:To make piercing without forming burrs by forming an annular groove on a plate by a die having an annular projection and piercing inside of the annular groove to forming side of the annular groove. CONSTITUTION:An annular projection having nearly the same diameter as the hole to be pierced on a plate B is formed on the upper face of a lower die member 1. The plate (b) is placed on the lower die member 1 and an upper die member 3 is pressed from above to plastic work an annular groove C on the plate B. Next, the plate is placed on a cylindrical die 4 which is nearly the same in inner diameter as the groove C of the plate B, and blanking is made from above by a punch 5. A step 6 is formed on the punch 5 and a face D is generated by pressing upper periphery of the hole E of the plate B. By this way, the generation of burrs on the periphery of the hole E can be prevented. |
