After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a short rack cutter of a practical length to be used. Cutter is again fed back again to depth and routine is repeated. Amount of teeth is controlled by the machine gearing, and pitch and pressure angle by the rack cutter. This technique is used for generation of external spur gears, being ideally suited for gear rack for Machine Tool Industry cutting large, double helical gears. For generating helical the teeth, the cutter slides tend at the gear tooth helix angle.
The hob is fed in to the gear blank to the correct depth and the two are rotated together as though in mesh. The teeth of the hob cut in to the work piece in successive purchase and each in a slightly different position. Each hob tooth cuts its own profile based on the shape of cutter , however the accumulation of these straight cuts generates a curved kind of the gear teeth, therefore the name generating procedure. One rotation of the work completes the trimming upto particular depth 
upto which hob can be fed unless the apparatus has a wide face.
This methodis specifically adopted to cutting large teeth which are tough to cut by formed cutter, and also to cut bevel-gear teeth. It is not widely used at the moment.
In gear planing procedure, the cutter includes true involute rack which reciprocates over the face of the blank and the blank rotates in the correct relationship to the longitudinal movement of the cutter as if both roll collectively as a rack and pinion. Initially the cutter is certainly fed into complete tooth depth with cutter reciprocating and blank stationary. Involute form is produced as the blank rotates and involute rack cutter feeds longitudinally.
In the other method, both roughening and completing cuts are taken with single pointed tools. The use of the formed tool for finishing is definitely impracticable for the larger pitches which are completed by a single pointed tool. The amount of cuts required is dependent upon how big is the tooth, amount of share to be eliminated, and the kind of material.