PURPOSE: To simply produce a cylindrical metal-made or ceramic-made blank having twisted longitudinal bores in the inner part by using dies and a die for extrusion forming having a core die fitting a center pin projected in the inner surface.

CONSTITUTION: Mixed powdery raw material such as Co, TiC, WC, TaNbC and ceramic raw material, for example, are pulverized and paraffine being lubricator is blended and sufficiently kneaded. The kneaded material is pressed in a space formed between the core die 11 and a die frame 6 in the arrow mark with an introducing die 5 and a die 4 to compact the kneaded material and form this green compact into a cylindrical shape with the die 4. The extruded product can be conformed to a center pin 7 on an eliptic shape cross sectional surface by using a spirally twisted hard alloy and steel, etc., with the sufficient plasticity of the kneaded material, and in this result, the bores 2 for coolant are formed in a bore blank 1 at a desired twist state and position and the die for extrusion formation is produced.