After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a brief rack cutter of a practical length to be used. Cutter is again fed back to depth and cycle is repeated. Number of teeth is managed by the machine gearing, and pitch and pressure angle by the rack cutter. This technique can be used for generation of external spur gears, being preferably fitted to cutting large, double helical gears. For making helical tooth, the cutter slides tend at the gear tooth helix angle.
The hob is fed into the gear blank to the proper depth and the two are rotated together as if in mesh. The teeth of the hob cut into the function piece in successive order and each in a gear rack for Machine Tool Industry china somewhat different placement. Each hob tooth cuts its profile based on the shape of cutter , but the accumulation of these directly cuts creates a curved kind of the gear teeth, therefore the name generating procedure. One rotation of the task completes the reducing upto particular depth upto which hob can be fed unless the apparatus has a wide face.
This methodis specially adopted to cutting large teeth which are challenging 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 movement of the cutter as though both roll with each other as a rack and pinion. Initially the cutter is fed into complete 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 definitely impracticable for the bigger pitches which are finished by a single pointed tool. The amount of cuts required is dependent upon the size of the tooth, quantity of stock to be removed, and the type of material.