After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus enabling a brief rack cutter of a practical duration to be utilized. Cutter is once again fed back again to depth and routine is repeated. Quantity of teeth is managed by the machine gearing, and pitch and pressure position by the rack cutter. This method can be used for generation of exterior spur gears, being preferably fitted to cutting large, double helical gears. For making helical tooth, the cutter slides are inclined at the gear tooth helix angle.
The hob is fed in to the gear blank to the proper depth and both are rotated together as though in mesh. The teeth of the hob cut into the function piece in successive gear rack for Machine Tool Industry purchase and each in a somewhat different position. Each hob tooth cuts its profile depending on the form of cutter , however the accumulation of these directly cuts creates a curved type of the gear teeth, hence the name generating process. One rotation of the task completes the reducing upto specific depth upto which hob is fed unless the gear includes a wide face.
This methodis specially adopted to cutting large teeth which are tough to cut by formed cutter, and to cut bevel-gear teeth. It is not widely used at present.
In gear planing process, the cutter consists of true involute rack which reciprocates across the face of the blank and the blank rotates in the correct relationship to the longitudinal motion of the cutter as if both roll collectively as a rack and pinion. At first the cutter is certainly fed into full tooth depth with cutter reciprocating and blank stationary. Involute shape is generated as the blank rotates and involute rack cutter feeds longitudinally.
In the other technique, both roughening and completing cuts are taken with single pointed tools. The use of the formed tool for finishing is usually impracticable for the larger pitches which are finished by an individual pointed tool. The amount of cuts required depends upon how big is the tooth, quantity of share to be removed, and the kind of material.