PURPOSE: To keep the outer diameter of a center pin exactly always and to prevent the fracture of the center pin by following method in which the center pin is inserted into the central hole preformed in a cake and the thermal expansion ob the center pin is prevented by the cold water flowing in said center pin.

CONSTITUTION: A cooling chamber 26 is formed in the inner part of the tip of a center pin 24, and in said chamber an inlet pipe 26a and an exit pipe are prepared. The lower end port of the inlet pipe 26a extends to the lower end of the cooling chamber 26. After the cake made by a cake producing device for a disk has been dropped onto a lower metal die 35, pressurized oil is introduced into the oil pressure chamber 43 in a subcylinder 38 from a conduit 45 by opening a switch valve 45a. The pressurized oil entering into the oil pressure chamber 43 raises a subpiston 39 slightly. When the subpiston 39 is raised, its lower end surface is separated from the upper end surface of a ram 41, and the pressurized oil entering into a flowing path 39a reaches the oil pressure chamber 40 in a main cylinder 28. The pressurized oil intering into the oil pressure chamber raises the main piston 30, and the lower metal die is press-operated against the upper metal die 20, thereby forming the cake into the disk.