| 摘要 |
PROBLEM TO BE SOLVED: To press a lock groove for engaging a locking piece of a locking device in a thin-walled pipe which is for a stay used for a head rest or the like and cannot be machined by cutting. SOLUTION: Bar-like cores (11 and 21) extending in the longitudinal direction and having a flat part (12) and groove parts (13, 22, and 23) are inserted in a pipe (1), lock grooves (2, 30 and 32) are machined on the pipe (1) by an upper die (6) or punches (11 and 21), the bar-like cores (11 and 21) are inverted and drawn out of the pipe (1) to form the stay (1) having the lock grooves (2, 30 and 32).
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