HELICAL BROACH AND INTERNAL GEAR MACHINING METHOD USING THE SAME

摘要

A helical broach which eliminates the need for a fixing means for fixing a workpiece during gear machining is provided. The helical broach includes: a plurality of cutting edges; a spiral flute formed between adjacent cutting edges to extend in a spiral manner with a predetermined helix angle with respect to an axial direction of the helical broach; and a gullet formed between adjacent cutting edges to extend with a predetermined helix angle with respect to a circumferential direction of the helical broach. In the helical broach, the expression: 0.5≤tan β/tan(α+β)≤0.7 is satisfied, wherein β is the helix angle of the spiral flute, and (90°−α) is the helix angle of the gullet with reference to a central axis of the helical broach. An internal gear machining method using the helical broach is also provided.