METHOD FOR FORMING SPIRAL GEAR OR THE LIKE

PURPOSE:To reduce the manufacturing cost of spiral gear, etc., by forging a raw material which is roughly worked into a rough gear shape into a tooth form between upper and lower die blocks, releasing this from a die with a knock-out in the lower die block and correcting it with a die having the same shaped lower die block as the lower die block. CONSTITUTION:The raw material W is formed into the spiral gear, etc., with hot forging by using the die 5 in the lower die block 2 and a punch 13 in the upper die block 3. Then, in a first process, a discoid raw material W is heated to roughly work it into the rough gear shape. In a second process, this is positioned between the lower die block 2 having under-cut tooth form and the knock-out 6 and the upper die block 3 having forming part to execute forging formation for tooth form. In a third process, the raw material is released from the die while rotating with the knock-out 6. In a fourth process, forging correction is executed with the die having the same shape of lower die block as the lower die block 2. By this method, working time can be shortened.