After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a brief rack cutter of a practical length to be used. Cutter is once again fed back again to depth and cycle is repeated. Number of teeth is managed by the device gearing, and pitch and pressure angle by the rack cutter. This method is used for generation of exterior spur gears, being preferably fitted to cutting large, dual helical gears. For making helical tooth, 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. One’s teeth of the hob cut in to the function piece in successive order and each in a somewhat different position. Each hob tooth cuts its own profile based on the form of cutter , but the accumulation of these directly cuts generates a curved kind of the gear teeth, thus the name generating procedure. One rotation of the task completes the slicing upto particular depth upto which hob is fed unless the gear has a wide face.
This methodis specially adopted to cutting large teeth which are challenging to cut by formed cutter, and to cut bevel-gear teeth. It isn’t 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 if both roll together as a rack and pinion. At first the cutter can be 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 technique, both roughening and completing cuts are taken with single gear rack for Machine Tool Industry pointed tools. The utilization of the formed tool for finishing is definitely 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 share to be eliminated, and the type of material.