| 摘要 |
PURPOSE:To form a split pin hole with high efficiency and at low cost by forming a recessed groove with cold forging at the end part of the thread of a bolt and by pressing with contraining the forming end part thereof with nearly globular punch in the split pin hole working of the bolt for automobile, etc. CONSTITUTION:The bolt blank with recessed groove at its tip is made by subjecting the thread end part 5a of a bolt to cold forging with the forming die 7 with projection part. The tip thereof is fitted a backing die 9 and pressed with the punch 8 having nearly globular recessed part 10 on its tip. The bolt tip is drawn to form a split pin hole. This method is highly efficient compared with the conventional punching machining method and the cost is reduced as well.
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