Abstract: Provided is a core metal including a shaft through-hole allowing a shaft to be inserted thereinto, and a resin locking portion allowing a resin to be locked and fixed, the shaft through-hole having a thicker periphery formed on a periphery of a prepared hole allowing the shaft to be inserted thereinto so as to project on any one of or both a front surface and a back surface of the metal material. The prepared hole and the thicker periphery are molded by subjecting a flat metal material automatically transferred with use of a press machine to drawing, drilling, and thickening.

Abstract: Provided is a core metal including a shaft through-hole allowing a shaft to be inserted thereinto, and a resin locking portion allowing a resin to be locked and fixed, the shaft through-hole having a thicker periphery formed on a periphery of a prepared hole allowing the shaft to be inserted thereinto so as to project on any one of or both a front surface and a back surface of the metal material. The prepared hole and the thicker periphery are molded by subjecting a flat metal material automatically transferred with use of a press machine to drawing, drilling, and thickening.