Patent ID: 8001819
Filing Date: 2011-08-23
Classification: B21D,B23P,Y10T

Abstract:
1. A piercing method using hydroforming comprising inserting a metal pipe into a split mold having a pierce punch able to be moved perpendicular to an axis of said inserted metal pipe or in a slanted direction, having a front part narrower than a center part, having around said front part a nut having an inside diameter larger than an outside diameter of said front part and smaller than an outside diameter of said center part, and having a secondary punch around said front part of said pierce punch at a position between said nut and said center part of said pierce punch; applying to said metal pipe an internal pressure and pipe axial direction pushing force or an internal pressure for hydroforming; making said pierce punch advance to pierce part of said metal pipe by a front part of said pierce punch; then making said nut advance while pushing said center part and said secondary punch arranged behind said nut; and pushing the surroundings of the pierced hole to the inner surface side of said metal pipe and embedding said nut in the metal pipe.