After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus gear rack for Machine Tool Industry china allowing a short rack cutter of a practical duration to be used. Cutter is again fed back to depth and cycle is repeated. Quantity of teeth is controlled by the device gearing, and pitch and pressure angle by the rack cutter. This technique is used for generation of external spur gears, being preferably fitted to cutting large, dual helical gears. For generating helical teeth, the cutter slides are inclined at the gear tooth helix angle.
The hob is fed into the gear blank to the correct depth and both 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 slightly different position. Each hob tooth cuts its own profile based on the shape of cutter , however the accumulation of these straight cuts produces a curved form of the gear teeth, therefore the name generating process. One rotation of the work completes the trimming upto particular depth upto which hob is usually fed unless the gear has a wide face.
This methodis specifically adopted to cutting large teeth which are difficult to cut by formed cutter, and also to cut bevel-gear teeth. It isn’t widely used at the moment.
In gear planing procedure, the cutter contains true involute rack which reciprocates over the face of the blank and the blank rotates in the right relationship to the longitudinal motion of the cutter as though both roll jointly as a rack and pinion. Initially the cutter can be 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 completing cuts are taken with single pointed tools. The usage of the formed tool for finishing is usually impracticable for the bigger pitches which are finished by an individual pointed tool. The number of cuts required depends upon the size of the tooth, quantity of share to be eliminated, and the kind of material.