FORMATION OF ROUGH FORGING FOR CRANK THROW

PURPOSE:To improve the dimension accuracy and productivity by forging simultaneously a forming surface for controlling a length of head part, and both front and rear sides through a roughly triangular wall-shaped projection, and also forming the head part by recessing and providing a notch on the center lower part and the bottom face. CONSTITUTION:A forging tool 22 of the lower position is provided on a receiving surface 21b of a receiving base 21 fixed to a bed or a floor surface, and also the forging tool 22 of the upper position is made to contact along a vertical guide surface 21a and charged. In this state, the forging tool 22 of the upper position is put by a tool manipulator 32 and a base material of an oblique line part is forged and worked. The tool 22 controls a height and a length of the head part as required and executes forging through pressure of a press by a forming surface 22a. Also, a triangular wall-shaped projection 22 provided in the center of the forming surface 22a forms a triangular groove-shaped notch. Accorcing to this method, the dimension accuracy of a throw material is improved, and also the productivity is improved.