Patent ID: 7150172

Claim:
A burring device, comprising: a work holder which has a burring hole and holds a work object; a pusher rod which rotatably supports a base end of a metal core which has a processing part on a tip end thereof; and a guide rod, positioned in front of the extended axis of said pusher rod, which has a guide surface on the tip end thereof which guides the tip end of said metal core towards the burring hole of said holder; wherein a lower hole of the work object is aligned with the burring hole in said holder; the tip end of said guide rod is made to correspond to the lower hole of said work object; said pusher rod is moved forward so that the metal core is made to contact the guide servers of said guide rod; said pusher rod is moved forward so that the tip end of said metal core is pressed into the lower hole of said work object in the circumferential edge of said lower hole is bent over, and a coining punch hole is formed concentrically with the burring hole of said work holder, positioned to the outside of said burring hole, and having a larger curvature radius than the curvature radius of the burring hole, and a coining punch is positioned to the outside of the extended axis of said burring hole.