After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a brief rack cutter of a practical duration to be utilized. Cutter is once again fed back again to depth and cycle is repeated. Amount of teeth is controlled by the machine gearing, and pitch and pressure angle by the rack cutter. This method can be used for generation of exterior spur gears, being ideally suited for cutting large, double helical gears. For making helical tooth, the cutter slides are inclined at the gear tooth helix angle.
The hob is fed into the gear blank to the proper depth and the two are rotated together as though in mesh. The teeth of the hob cut into the function piece in successive purchase and each in a somewhat different position. Each hob tooth cuts its profile based on the form of cutter , but the accumulation of these directly cuts generates a curved kind of the gear teeth, hence the name generating process. One rotation of the task completes the trimming upto specific depth upto which hob is definitely fed unless the gear has 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 gear rack for Machine Tool Industry china 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. At first the cutter is certainly fed into complete tooth depth with cutter reciprocating and blank stationary. Involute shape 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 number of cuts required is dependent upon how big is the tooth, amount of share to be removed, and the kind of material.