Importance

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Abstract

In a method for increasing the thickness of an outer peripheral portion of a metallic disc material, a first forming die is prepared so as to have a first groove portion on an outer periphery thereof for receiving the metallic disc material. The first groove portion has a pair of side walls and a bottom wall therebetween. The side walls has inclined surfaces facing each other so as to increase the width of the first groove portion toward the outer peripheral portion of the metallic disc material. One of the side walls has a greater length from the bottom wall of the first groove portion than that of the other side wall. The first cylindrical forming die is pressed against the outer peripheral portion of the metallic disc material in a radial direction to form a thickened outer peripheral portion of the metallic disc material. When the first forming die is pressed against the outer peripheral portion of the metallic disc material in the radial direction, the inclined surface of the one side wall of the first forming die is brought into contact with one surface of the outer peripheral portion of the metallic disc material, so that the outer peripheral portion of the metallic disc material is bent in a direction along the inclined surface of the one side wall while molding the thickened outer peripheral portion of the metallic disc material in the first groove portion.

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First Claim