| 摘要 |
PURPOSE:To improve the quality of a through hole by using the punch having the cutting blade part in parallel to the working direction at one part of the cutting blade part and a regular shearing angle, and performing the side cutting of the cutting blade part having three sides repeatedly in the space with a die as well. CONSTITUTION:The punch 19 providing a regular shearing angle as well as having the cutting blade part in parallel to the nibbling direction is used as for the punch. In this case, the high and low difference delta in the upper end part 55 of the front part and the lower end part 57 of the rear part is made larger than a plate thickness (t). The nibbling is performed by ascending the front part cutting blade by stopping its descent prior to its abutting to a work plate stock W and repeating the side cutting descent with the cutting blade part having three sides excepting the front face in the progressing direction. The cutting blade including the upper end part 55 does not perform the shearing while under the whole working, and after the lower end part 57 being sheared once the shearing is performed with the right and left both side cutting blades only. Consequently the generation of an indentation while under working is eliminated and the quality of the through hole is improved.
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