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Pub. No.:    WO/2018/124254    International Application No.:    PCT/JP2017/047146
Publication Date: Fri Jul 06 01:59:59 CEST 2018 International Filing Date: Thu Dec 21 00:59:59 CET 2017
IPC: B21D 19/08
F28F 9/04
Applicants: T.RAD CO., LTD.
Inventors: TAKASE Masaaki
高瀬 正明
Provided is a highly flexible and simple burring method having a wide range of applications, regardless of the size of flat holes or the burring height around the edges of same during the process of burring metal plates. This method performs burring on a metal plate by: arranging one surface of the metal plate on the surface of a die having a vertical inner circumferential surface relative to a flat surface of the die and having a cavity having a flat cross-section inner circumference that is horizontal to the flat surface; and pressing a flat burring punch from the other surface of the metal plate towards the cavity, said burring punch having a vertical outer circumferential surface relative to the die flat surface. The punch has a flat cross-section parallel to the flat surface and, in a state in which the punch is pressed towards the cavity having the metal plate therebetween, the interval between a pair of vertical outer surfaces parallel to the pressing direction of the punch and inner surfaces of the die cavity facing same, at positions at both ends of the punch cross-section in the longitudinal direction, is set smaller than the gap between the outer surface of the punch parallel to the pressing direction and the inner surface of the die cavity facing same, at positions at both ends of the cross-section in the width direction.