| 摘要 |
PURPOSE:To improve the accuracy of punch blanking, by chamfering the angular parts of a core bisected while giving a taper and smoothening the movement of the core in a square pipe. CONSTITUTION:In a titled piercing die, an upper core 6 and a lower core 7 bisected with the contact surface slanted downward to an upper core holding bar 9 and a lower core holding bar 11 are inserted into a square pipe 2 and a hole is piercd in the pipe 2 by punching. Holding bars 9, 10 are attached to cores 6, 7 separately so that the core 6 is held to allow vertical sliding and the core 7 is held so as to be slid in the axial direction. A chute 8 for sucking scrap connected to a scrap sucking pipe is formed in the cores 6, 7. The radius of curvature of chamfering of upper angular part of the core 6 is made larger than that of the inner angular part of the pipe 2. At the same time, the radius of curvature of chamfering of lower angular part of the core 7 is made smaller than that of the inner angular part of the pipe 2. |
