After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a short rack cutter of a practical length to be used. Cutter is once again fed back again to depth and cycle is repeated. Number of teeth is controlled by the device gearing, and pitch and pressure position by the rack cutter. This method is used for generation of exterior spur gears, being preferably suited for cutting large, double helical gears. For generating helical the teeth, the cutter slides tend at the apparatus tooth helix angle.
The hob is fed in to the gear blank to the correct 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 placement. Each hob tooth cuts its profile based on the shape of cutter , however the accumulation of these straight cuts produces a curved kind of the gear teeth, hence the name generating process. One rotation of the task completes the slicing upto specific depth upto which hob is fed unless the apparatus includes a wide face.
This methodis gear rack for Machine Tool Industry specially adopted to cutting large teeth which are hard to cut by formed cutter, and also to cut bevel-gear teeth. It is not widely used at present.
In gear planing process, the cutter includes 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. At first the cutter is usually 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 usage of the formed device for finishing is certainly impracticable for the bigger pitches which are finished by an individual pointed tool. The amount of cuts required is dependent upon the size of the tooth, quantity of share to be taken out, and the kind of material.