FORMING METHOD OF SHAFT-SHAPED PARTS CONTRACTED IN CENTRAL PART

摘要

PURPOSE:To produce easily and inexpensively a shaft-shaped part which is contracted in he central part by using segmental dies having large-diameter spaces in the upper and lower parts and a small-diameter space in the intermediate part and subjecting stock to extrusion molding while acting a back pressure thereto then subjecting the stock to upsetting. CONSTITUTION:The circular cylindrical stock is heated and is inserted into the segmental dies 4 having the large-diameter spaces 4a, 4b to be fitted respectively with the upper punch 1 and the power punch 2 and having the small- diameter space 4c in the intermediate part in a forming device consisting in holding said dies 4 via a spacer 8 on a bed 6. The stock is then subjected to forward extrusion by lowering the upper punch 1 via a slide 7. The top end of the extruded stock contacts with the punch 2 by which the stock is diametrally expanded. The lower slide 5 is operated and the punch 2 is lowered while the extruding pressure is maintained when said pressure attains the prescribed pressure. The punch 2 is raised to upset the lower part of the stock upon ending of the extrusion when the punch 1 arrives at the prescribed position. The final product A is thus obtd.