| 摘要 |
PROBLEM TO BE SOLVED: To form a shaft-shaped parts, having a contraction in its intermediate section by a cold forging with a stable precision and to improve a yield and production efficiency. SOLUTION: A shaft-shaped billet W is set in a workpiece set mechanism 15 of a die unit, where as an upper punch 18 drops, it pushes a segment die 5 to drop along the tapered face t of the inner periphery of an opening/closing guide member 4, and the segment die 5 is closed. Then an upper punch 18 is dropped, while the peripheral side of the shaft-shaped billet W is bound by the segment die 5, a compressive load is applied in an axial direction by the upper punch 18 and a knockout pin 14, then the shaft-shaped parts are formed, whose intermediate section are contracted in accordance with the shape of a forming face s of the split die 5.
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