After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a short rack cutter of a practical length to be used.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 once again fed back again to depth and cycle is repeated. Quantity of teeth is controlled by the machine gearing, and pitch and pressure position by the rack cutter. This technique is utilized for generation of external spur gears, being ideally suited for cutting large, double helical gears. For producing helical the teeth, the cutter slides tend at the apparatus tooth helix angle.
The hob is fed into the gear blank to the correct depth and both are rotated together as though in mesh. The teeth of the hob cut into the function piece in successive order and each in a somewhat different placement. Each hob tooth cuts its own profile depending on the form of cutter , but the accumulation of these straight cuts creates a curved form of the gear teeth, therefore the name generating process. One rotation of the work completes the reducing upto particular depth upto which hob is fed unless the apparatus includes a wide face.
This methodis specially adopted to cutting large teeth which are difficult to cut by formed cutter, and also to cut bevel-gear teeth. It isn’t widely used at the moment.
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 right relationship to the longitudinal movement of the cutter as though both roll jointly as a rack and pinion. Initially the cutter is 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 technique, both roughening and completing cuts are taken with single pointed tools. The use of the formed device for finishing is impracticable for the bigger pitches which are gear rack for Machine Tool Industry china completed by a single pointed tool. The number of cuts required is dependent upon the size of the tooth, amount of stock to be removed, and the type of material.