COLD FORGING DIE FOR DIAGONAL TOOTH PROFILE PARTS

PROBLEM TO BE SOLVED: To provide parts which is free from any part to be chipped in a diagonal tooth profile, and excellent in quality by forming a guide surface to turn a work in the same direction as that of a helix of the diagonal tooth profile on at least a part of a surface having a total tooth height of a diagonal tooth forming part of one end face of a die. SOLUTION: A work is placed on an upper end face of a flat die 1, and a punch is lowered from an upper part with the prescribed pressure. The work is intervened between a supporting part and a holding part at its edge parts, and its center part is pushed into a diagonal tooth forming part 1a. In the beginning of the forming process, when a guide surface 1f to the flat die 1 is inclined against the horizontal plane, the pressing force is divided into the component parallel to the guide surface 1f and the component perpendicular to the guide surface 1f. Therefore the force parallel to the guide surface 1f is applied to the work. Even in the beginning of the forming process, the work is guided by the guide surface 1f by this force and rotated in the same direction as that of a helix of the outer diagonal tooth profile, and the material of the work is sufficiently supplied.