PUNCHING METHOD AND PUNCHING DEVICE EMPLOYING HYDRO-FORM AND HYDRO-FORMED PART AND STRUCTURE BODY

摘要

In a punching method also applicable to a thin hydro-form molding, a short tube member is eliminated when a nut for tightening a bolt is fixed to a hydro-form molding, the degree of difficulty of hydro-form molding does not rise when a nut is fixed, and the nut is lengthened so that sufficient strength 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 the pipe axis, has a thinner diameter at the distal end than at the middle portion and is provided, on the periphery of the distal end, with nuts having an inside diameter larger than the outside diameter at the distal end but smaller than the outside diameter at the middle portion. After hydro-form molding is performed, the punch is advanced and a portion of the hydro-form molding 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.