MANUFACTURE OF HOLLOW GEAR

PURPOSE:To constrain a burr and to reduce the breakdown of a die by providing a recessed part at the end face part of the opposite side to a punch of a solid material and forming a curvature part at the angular part sliding with a die. CONSTITUTION:A solid material W1 is provided with recessed parts H1, H2 biting to the inner side from both end faces. The recessed part H1 reduces the load exerted on a punch at a hole opening stage, the recessed part H2 is provided on the end face of the opposite side to the end face on which the recessed part H1 is provided, its outside max. diameter is larger than the outer diameter of the punch used in the hole opening stage and in the shape of about the truncated cone gradually reducing toward the inner part of the material W1. A curvature part R1 is formed with the clearance X2 of a punch 3 and die 5 and a gap E, so the fear of causing a burr is eliminated with the metal of the material being pulled in to a clearance X2. A curvature part R2 can evade the generation of a gnawing on the part of the vicinity of the tooth part forming part 5a of the die 5.