METHOD FOR FORMING BURRING AND DIE DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a method for forming burring and a die device by which a final collar is formed high and into uniform thickness by obtaining the uniform thickness without loading concentrated tensile load in the preforming of a metal plate. SOLUTION: When a part of the metal plate 27 where the burring is performed is preformed, by using a knock-out collar provided with a recessed part for relief on its bottom end surface, the metal plate 27 is pressed with a forming punch 20 in the state where the metal plate 27 is not held with the knock-out collar 7 and the forming punch 20, and a stretch forming part 32 is preformed.