FORGING METHOD OF CROWNING GEAR TOOTH OF HELICAL GEAR AND FORGING DEVICE THEREFOR

PROBLEM TO BE SOLVED: To form a crowning gear tooth only in forging by forming a gear tooth forming cavity with upper/lower dies, pressing a stock with upper/lower punches to fill the gear tooth forming cavity, forging the gear tooth and pulling out a gear while relatively moving a rotatable die along the gear. SOLUTION: A stock A1 is fitted into a mandrel 20 and set in a lower die 15. By bringing an upper die 18 into tight contact with the lower die 15, a gear tooth forming cavity is formed to the outer periphery of the stock A1. Next, an upper punch 21 is descended, and the stock A1 is pressed by a lower punch 19 and the upper punch 21 to fill the gear tooth forming cavity, a helical gear B1 is forged. Then, an upper die holder 12 is ascended, and the upper die 18 rotatably held is turned along the gear tooth of the helical gear B1 to pull out. Finally, the upper and lower punches 21 and 19 are ascended, and the helical gear B1 is pulled out from the lower die 15 while turning it.