A cylindrical cutting tool built as a worm with flutes, or gashes, cut across its threads to form rows of teeth, each sharpened on its face. One hob cuts any tooth count of the same module or pitch and pressure angle. Hobs come in single or multiple starts and in accuracy classes, and they are shifted axially during a run so wear spreads along the whole tool before resharpening.
Hob's due for a sharpen, the profile trace is starting to show it, and shift it to fresh teeth for the next lot.
Also heard as
- gear hob
- hob cutter
Related terms
Hobbing
Generating gear teeth with a rotating worm-shaped cutter that turns in step with the blank.
Rack
A straight bar with gear teeth along it, which turns a pinion's rotation into straight-line travel.
Ghost frequency
A gear noise tone that matches no tooth count in the box, left behind by errors in the cutting machine.
Scallops
Shop word for the small ridges a hob leaves across and along each tooth flank, visible as a fine texture.