After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus enabling a short rack cutter of a practical duration to be utilized. 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 technique is utilized for generation of exterior spur gears, being ideally suited for cutting large, dual helical gears. For making helical tooth, the cutter slides are inclined at the apparatus tooth helix angle.
The hob is fed into the gear blank to the correct 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 slightly different placement. Each hob tooth cuts its profile depending on the form of cutter , however the accumulation of these directly cuts generates a curved form of the gear teeth, thus the name generating procedure. One rotation of the work completes the cutting upto specific depth upto which hob is fed gear rack for Machine Tool Industry unless the apparatus has a wide face.
This methodis specially adopted to cutting large teeth which are difficult to cut by formed cutter, and also to cut bevel-gear teeth. It isn’t 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 motion of the cutter as if 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 form 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 use of the formed device for finishing is certainly impracticable for the larger 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.