Define the Gear Hobbing

This is the most productive of all the gear production processes. However, it can only be used for producing spur gears and worn gears. It cannot be used to cut internal gears and it cannot work up a shoulder.

Figure: Generation of external gear teeth by Hobbing: (a) helical tooth and (b) worm wheel

The hob is used to generate the involutes teeth here. The hob is basically a straight cylindrical tool around which a thread with the same cross section as the rack tooth has been helically wound. This hob is then rotated with the gear blank fed onto the hob according to the depth of cut. The helix pattern of hob as it rotates is the same as that of the rack moving laterally.