PURPOSE:To prevent a double punching caused by a blank lift-performance, and at the same time, to design a metal mold easily at a low price by extending a drawing section after punching the external form of a rotor core and contracting a diameter of the punched hole. CONSTITUTION:In the process III, a forming-work is applied to a bead-like projected ringed drawing section 13 provided with the internal diameter (d1) larger than a diameter (d2) of the external form 15 of a rotor core punched in the after-process, and the drawing section 13 and a concentric shaft hole 14 are punched on a shaft center section in the process IV. In the process V, the external form 15 of the rotor core R is concentrically punched with the drawing section 13 in the diameter (d2) smaller than the internal diameter (d1) of the drawing section 13, and is punched off as the rotor core R. In the process VI, the drawing section 13 is thrusted to pt it back to the flat, and at that time, the diameter (d2) becomes a contraction diameter hole 16 with a smaller diameter (d3) by the drawing section extended along the shaft center.
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