Press die

A press die for piercing operation having a lower die and an upper die provided on said lower die;

• said press die comprising:
• means defining a hollow bore in one of said lower and upper dies, for functioning as a female die;
• a movable pad interposed between the lower die and the upper die to hold a workpiece between the pad and the female die against the lower die when the upper die is moved toward the lower die, said pad having an insertion hole therethrough coaxial with the hollow bore;
• a punch passed through the insertion hole;
• punch pressing means for driving the punch against the workpiece so as to cause the punch to be inserted into the hollow bore to thereby carry out the piercing operation on the workpiece;
• a tubular elastic member inserted in said insertion hole and accommodating the punch inserted therethrough to be interposed between the punch and an inner surface of insertion hole of said pad to support the punch;
• and
• a projecting tip having a smaller cross sectional area than a cross sectional area of the punch, provided on an end of the punch for deforming said workpiece to produce a bulge on the workpiece prior to the piercing operation and to be influenced by curvature of the bulge to shift the punch against elastic resistance of the elastic member to an optimum state wherein the projecting tip and the hollow bore are in accurate coaxial alignment therebetween at the instant of the piercing operation.