After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a short rack cutter of a practical duration to be used. Cutter is again fed back again to depth and cycle is repeated. Quantity of teeth is managed by the machine gearing, and pitch and pressure position by the rack cutter. This method is utilized for generation of external spur gears, being ideally suited for cutting large, dual helical gears. For producing helical teeth, the cutter slides are inclined at the gear 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. 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 based on the form of cutter , however the accumulation of these directly cuts produces a curved type of the gear teeth, therefore the name generating process. One rotation of the task completes the reducing upto certain depth upto which hob can be fed unless the apparatus has a wide face.
This methodis specifically adopted to cutting large teeth which are tough to cut by formed cutter, and also to cut bevel-gear teeth. It isn’t widely used at present.
In gear planing process, the cutter consists of true involute rack which reciprocates across the face of the blank and the blank rotates in the correct relationship to the longitudinal motion of the cutter as if both roll with each other as a rack and pinion. Initially the cutter is definitely fed into complete tooth depth with cutter reciprocating and blank stationary. Involute form is gear rack for Machine Tool Industry generated as the blank rotates and involute rack cutter feeds longitudinally.
In the other technique, both roughening and completing 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 how big is the tooth, quantity of stock to be eliminated, and the kind of material.