Patent ID: 7934409
Filing Date: 2011-05-03
Classification: B21C,B21J,Y10T

Abstract:
1. A method for making a circular flanged hole in a metal sheet, comprising: punching through a metal sheet to form a preformed hole by a first punch; punching a circumferential portion of the preformed hole by a second punch to form a protruded portion, and a size of the second punch is larger than that of the first punch; and forming a flange surrounding the preformed hole by a third punch, wherein the third punch comprises a shank portion and a non-circular cross section drill portion extending from one end of the shank portion, and the shank portion is cylindrical and has a circumference larger than that of the non-circular cross-section drill portion, wherein the flange is formed by rotating the third punch with the non-circular cross-section drill portion to displace the material adjacent to the performed hole.