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completion of 1 or two teeth, the blank and gear rack for Machine Tool Industry cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus enabling a brief rack cutter of a practical duration to be utilized. Cutter is again fed back to depth and cycle is repeated. Number of teeth is managed by the device gearing, and pitch and pressure position by the rack cutter. This method is used for generation of external spur gears, being preferably suited for cutting large, double helical gears. For generating helical tooth, 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 the two are rotated together as though in mesh. One’s teeth of the hob cut into the function piece in successive order and each in a somewhat different position. Each hob tooth cuts its profile depending on the shape of cutter , but the accumulation of these directly cuts produces a curved type of the gear teeth, therefore the name generating procedure. One rotation of the task completes the slicing upto specific depth upto which hob is fed unless the gear includes 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 is not widely used at the moment.
In gear planing process, the cutter consists of accurate involute rack which reciprocates across the face of the blank and the blank rotates in the correct relationship to the longitudinal movement of the cutter as though both roll with each other as a rack and pinion. At first the cutter is certainly fed into full tooth depth with cutter reciprocating and blank stationary. Involute shape is produced as the blank rotates and involute rack cutter feeds longitudinally.
In the other method, both roughening and finishing cuts are taken with single pointed tools. The usage of the formed tool for finishing is impracticable for the larger pitches which are finished by a single pointed tool. The number of cuts required is dependent upon the size of the tooth, quantity of share to be eliminated, and the kind of material.