| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and device for manufacturing a lock bolt for civil engineering that has a recess for expansion without performing drawing work to a large machining degree in the center of the tube, with both tube ends left in the round shape. SOLUTION: A steel tube with one end closed is set in a hydraulic forming device equipped with an outer die 11 for bulging, with a pressure fluid imparted from a pressure fluid feeding source 17 to preliminarily form a cross section that has a part bulged out eccentrically over the longitudinal direction except both ends. Then, with the eccentric bulged part held in a receiving die 12, press working is performed using a press die 13 having a blade-shaped cross section to form the recess. After that, draw-forming is performed on the entirety by means of a drawing die 15 having a diameter nearly the same as the outer diameter of the base tube. COPYRIGHT: (C)2004,JPO
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