After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a short rack cutter of a practical size to be utilized. Cutter is once again fed back to depth and routine is repeated. Number of teeth is controlled by the device gearing, and pitch and pressure angle by the rack cutter. This technique is utilized for generation of exterior spur gears, being ideally fitted to cutting large, dual helical gears. For creating helical teeth, the cutter slides tend at the gear tooth helix angle.
The hob is fed in to the gear blank to the proper depth and the two are rotated together as if in mesh. The teeth of the hob cut in to the function piece in successive order and each in a slightly different position. Each hob tooth cuts its profile based on the shape of cutter , but the accumulation of these directly cuts produces a curved form of the gear teeth, therefore the name generating process. One rotation of the task completes the cutting upto certain depth upto which hob is fed unless the gear includes a wide face.
This methodis specially gear rack for Machine Tool Industry china 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 present.
In gear planing procedure, the cutter consists of accurate 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 though both roll together as a rack and pinion. Initially the cutter is fed into complete tooth depth with cutter reciprocating and blank stationary. Involute form is generated 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 utilization of the formed tool for finishing is impracticable for the bigger pitches which are completed by a single pointed tool. The amount of cuts required is dependent upon the size of the tooth, quantity of stock to be taken out, and the kind of material.