Patent ID: 7406852
Filing Date: 2008-08-05
Classification: B21J

Abstract:
1. An upsetting method using an upsetting apparatus provided with a fixed die for securing a bar-shaped raw material, a guide having an insertion hole for receiving and holding a diameter expansion scheduled portion of the raw material in a buckling preventing state, and a punch, wherein a diameter expansion preventing protruded portion protruded in an axial direction of the guide is integrally formed at a part of a tip end portion of the guide, the method comprises: inserting and holding the diameter expansion scheduled portion of the raw material secured to the fixed die in the insertion hole of the guide; and subsequently expanding the diameter expansion scheduled portion of the raw material exposed between the tip end portion of the guide and the fixed die in a state in which diameter expansion of a contacting portion of the diameter expansion scheduled portion in contact with the diameter expansion preventing protruded portion is restrained by moving the guide in a direction opposite to a moving direction of the punch while moving the punch and pressurizing the diameter expansion scheduled portion of the raw material with the punch in an axial direction thereof such that expansion of the raw material is prevented at the part of the tip end portion of the guide having the expansion prevention protruded portion, but not prevented at other parts of the tip end portion of the guide.