PURPOSE: To improve the fragility of a core by using a high Si content ferrosilicon for its internal part while using a low Si content ferrosilicon for its circumference part.

CONSTITUTION: A metal mold 5 for extrusion molding has at its lower end an extruding opening 8 with a triangular section. A core circumference material layer 6, made from a mixture of a low Si content (1W2wt% after sintering) ferrosilicon powder, a binder, a thermoplastic plasticizer and an organic solvent, is provided to the inner surface of the metal mold 5 which is then filled with a mixture 7 of a high Si content (6.5wt% after sintering) ferrosilicon powder and the minimum of a low evaporation temperature organic solvent. Then, using a press 4, the material layer 6 and the mixture 7 are extruded from the extruding opening 8 while heating the mold 5 by means of a heating coil placed around the mold. An extruded ferrosilicon rod 9 is cut and sintered to obtain a dot printer head core 2 with its circumference part made from a low Si content ferrosilicon 6' and with the internal parts made from a high Si content ferrosilicon 7'.