| 摘要 |
PURPOSE:To shorten the working time by pressing the uneven roughened surface of a dressing tool to the surface of the outer periphery of through hole and by peeling the mill scale in linking with piercing operation. CONSTITUTION:A piercing punch 13 is provided on the movable upper die 1 of press machine and also dressing punch 14 is arranged on the outer periphery of the punch 13. The upper face of the punch 14 is fixed to the lower face of a holder 12 and roughened surface is formed by plural small projections on the lower face thereof. A presser 16 and sub-presser 15 are brought into contact with steel plate 5 by placing the steel plate 5 on the placing face 33 of the lower die 3 and by descending the upper die 1. Simultaneously with piercing punch 13 forming through hole by the descent of shank 11 a pressure force is applied by the lower face 14a of the dressing punch 14 on the outer peripheral surface of the through hole. In this case, due to the mill scale of the above of the surface of the steel plate 5 being peeled a nut can be welded in good state to the steel plate 5 thereafter. With this method, the processing time in piercing and welding is shortened.
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