PURPOSE: To enhance strength at the gate cutter part of a temporary shaft and to simplify the machining profile of lower die by disposing a groove type gate part on the outer circumference of the upper cutter of the temporary shaft thereby constituting the gate mainly of the temporary shaft.

CONSTITUTION: Required number of rotor cores 1 are stacked on a temporary shaft 3 and a predetermined quantity of molten conductor material is poured into the molten sump 7a of a sleeve 7. A lower die 4 is then disposed at a predetermined position and the rotor cores 1 stacked on the temporary shaft 3 are mounted thereon. Consequently, a gate 3a to be filled with conductor material 2 is formed. An upper die 5 preset on a moving table 6 is then lowered to press the rotor cores 1. When a press plunger 8 is lifted under this state, molten conductor material flows through the gate 3a, the lower die 4 and the rotor cores 1 and filled in the upper die 5. When the rotor cores 1 are mounted on a rotor base 10 and the temporary shaft 3 is pressed by means of a rod 9, the temporary shaft 3 lowers to cut the gate 3a and separates a biscuit 2e.