| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of forming a through hole by which a beautiful through hole in which the production of burrs at the bottom part of a hollow shaft is remarkably suppressed is easily formed. SOLUTION: A recessed part 8 on the peripheral part of the bottom of which the edge part 8a is formed on the surface of the one side by pressing a pressing punch 7 having an edge on the outer peripheral part at the tip against the bottom part 2a of the hollow shaft 2. When a projecting part 9 formed on the surface of the other side at this time is pushed back with a pressing tool 10, by forming the through hole by breaking the projecting part off from the edge part 8a in the recessed part 8, the production of the burrs is remarkably suppressed and the beautiful through hole is easily formed. COPYRIGHT: (C)2004,JPO&NCIPI
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