After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a short rack cutter of a practical size to be utilized. Cutter is 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 is used for generation of external spur gears, being ideally fitted to cutting large, double gear rack for Machine Tool Industry china helical gears. For creating helical the teeth, the cutter slides tend at the apparatus tooth helix angle.
The hob is fed into the gear blank to the proper depth and both are rotated together as though in mesh. One’s 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 shape of cutter , however the accumulation of these directly cuts generates a curved type of the gear teeth, therefore the name generating process. One rotation of the work completes the cutting upto certain depth upto which hob can be fed unless the gear has a wide face.
This methodis specifically 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 the moment.
In gear planing process, the cutter includes accurate involute rack which reciprocates across the face of the blank and the blank rotates in the right relationship to the longitudinal motion of the cutter as though both roll together 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 generated as the blank rotates and involute rack cutter feeds longitudinally.
In the other method, both roughening and completing cuts are taken with single pointed tools. The utilization of the formed device for finishing can be impracticable for the larger pitches which are completed by a single pointed tool. The amount of cuts required depends upon how big is the tooth, amount of stock to be removed, and the type of material.