What is a threaded and fluted hardened steel cutter, resembling a tap, used in a lathe for forming the teeth of screw chasers, worm wheels, etc called?

hob — (Mech.) A threaded and fluted hardened steel cutter, resembling a tap, used in a lathe for forming the teeth of screw chasers, worm wheels, etc. (Webster's 1913.)

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