| 摘要 |
<p>In a punching method also applicable to a thin hydro-form molding, a shor t tube member is eliminated when a nut for tightening a bolt is fixed to a h ydro-form molding, the degree of difficulty of hydro-form molding does not r ise when a nut is fixed, and the nut is lengthened so that sufficient streng th can be assured when the bolt is tightened. A metal pipe is inserted into a split die with a punch which is movable perpendicularly or obliquely to th e pipe axis, has a thinner diameter at the distal end than at the middle por tion and is provided, on the periphery of the distal end, with nuts having a n inside diameter larger than the outside diameter at the distal end but sma ller than the outside diameter at the middle portion. After hydro-form moldi ng is performed, the punch is advanced and a portion of the hydro-form moldi ng is punched and then the nut is buried in the metal pipe while the nut is pushed at the middle portion arranged in the rear of the nut.</p> |
