After completion of 1 or two teeth, the blank and gear rack for Machine Tool Industry cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a short rack cutter of a practical duration to be used. Cutter is once again fed back to depth and routine is repeated. Quantity of teeth is managed by the device gearing, and pitch and pressure position by the rack cutter. This technique can be used for generation of external spur gears, being ideally fitted to cutting large, dual helical gears. For making helical the 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 work piece in successive purchase and each in a somewhat different placement. Each hob tooth cuts its own profile based on the shape of cutter , but the accumulation of these directly cuts creates a curved type of the gear teeth, therefore the name generating procedure. One rotation of the task completes the slicing upto particular depth upto which hob is certainly 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 present.
In gear planing procedure, the cutter includes true involute rack which reciprocates across the face of the blank and the blank rotates in the right relationship to the longitudinal movement of the cutter as though both roll collectively 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 technique, both roughening and finishing cuts are taken with single pointed tools. The utilization of the formed device for finishing can be impracticable for the bigger pitches which are completed by an individual pointed tool. The amount of cuts required depends upon how big is the tooth, amount of stock to be removed, and the kind of material.