After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a short rack cutter of a practical duration to be utilized. Cutter is once again fed back to depth and cycle is repeated. Quantity of teeth is managed by the device gearing, and pitch and pressure angle by the rack cutter. This method is used for generation of exterior spur gears, being ideally suited for cutting large, dual helical gears. For producing helical 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 both are rotated together as though in mesh. The teeth of the hob cut into the work piece in successive order and each in a slightly different position. Each hob tooth cuts its profile based on the form of cutter , however the accumulation of these straight cuts gear rack for Machine Tool Industry produces a curved form of the gear teeth, hence the name generating procedure. One rotation of the task completes the reducing upto particular depth upto which hob is definitely fed unless the apparatus has a wide face.
This methodis specially adopted to cutting large teeth which are challenging to cut by formed cutter, and to cut bevel-gear teeth. It is not widely used at present.
In gear planing procedure, the cutter contains accurate involute rack which reciprocates over the face of the blank and the blank rotates in the correct relationship to the longitudinal motion of the cutter as though both roll collectively as a rack and pinion. At first the cutter is usually fed into full 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 technique, both roughening and finishing cuts are taken with single pointed tools. The usage of the formed tool for finishing is impracticable for the larger pitches which are finished by an individual pointed tool. The amount of cuts required depends upon the size of the tooth, amount of share to be eliminated, and the kind of material.