Piercing die whose punch has different amounts of chamfer at different outer peripheral edge portions

摘要

A piercing die including a punch and a die cooperating with each other to effect a piercing operation on a metallic workpiece sheet, the punch having an outer peripheral edge having a closed profile at a working end thereof. The outer peripheral edge of the punch has a first and a second chamfered portion which are formed such that the amount of chamfer of the first chamfered portion is larger than that of the second chamfered portion. The first and second chamfered portions are formed along large-curvature and small-curvature portions of the closed profile of the punch, respectively, and/or along acute and obtuse outer peripheral portions of the punch whose working end face is inclined with respect to the direction perpendicular to the piercing direction. A piercing method using the punch and die is also included.