Camshaft, method of manufacturing cam for camshaft, and method of manufacturing shaft for camshaft

A method of manufacturing a cam for a camshaft of an engine, comprising the steps of:

• performing preliminary profile upsetting on a forging blank having a volume which is greater than a final product by a predetermined amount, thereby forming a first cold-forged body which is thicker than the final product,
• said first cold-forged body having a rough shape which has an outer profile greater than that of the final product;
• performing profile drawing on said first cold-forged body to form a second cold-forged body, said second cold-forged body having excessive material that has flowed along a profile of an outer circumferential surface that corresponds to a shape of the final product being formed as a burr on an outer surface thereof;
• punching said second cold-forged body to form inner and outer surfaces simultaneously thereon, thereby forming a third cold-forged body with said burr removed from the outer surface, said third cold-forged body further having a relief hole which is smaller in diameter than a shaft insertion hole for the camshaft;
• pressing said third cold-forged body to form a fourth cold-forged body having a predetermined thickness and including an excessive material formed as a burr on the inner surface thereof, while an outer circumferential surface of said third cold-forged body is constrained by a die surface;
• punching said fourth cold-forged body to remove said burr from said inner surface, thereby forming a fifth cold-forged body having a hole corresponding to said shaft insertion hole;
• and
• ironing said fifth cold-forged body simultaneously on inner and outer surfaces thereof, thereby forming a final product.