After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus enabling a brief rack cutter of a practical length to be used. Cutter is once again fed back again to depth and routine is repeated. Quantity of teeth is managed by the machine gearing, and pitch and pressure position by the rack cutter. This method can be used for generation of external spur gears, being preferably suited for cutting large, dual 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 the two are rotated together as if in mesh. One’s teeth of the hob cut in to the function piece in successive purchase and each in a slightly different position. Each hob tooth cuts its profile based on the form of cutter , however the accumulation of these straight cuts produces a curved form of the gear teeth, therefore the name generating procedure. One rotation of the task completes the slicing upto particular depth upto which hob is usually fed unless the gear includes a wide face.
This methodis specially adopted to cutting large teeth which are hard to cut by formed cutter, and to cut bevel-gear teeth. It is not widely used at present.
In gear planing process, 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 though both roll collectively as a rack and pinion. Initially 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 tool for finishing is impracticable for the bigger pitches which are gear rack for Machine Tool Industry finished by a single pointed tool. The amount of cuts required depends upon how big is the tooth, amount of stock to be taken out, and the type of material.