After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus enabling a short rack cutter of a practical length to be utilized. Cutter is once again fed back again to depth and routine is repeated. gear rack for Machine Tool Industry china Amount of teeth is controlled by the device gearing, and pitch and pressure position by the rack cutter. This method is utilized for generation of external spur gears, being preferably fitted to cutting large, dual helical gears. For making helical teeth, the cutter slides tend at the gear tooth helix angle.
The hob is fed into the gear blank to the correct depth and both are rotated together as if in mesh. One’s teeth of the hob cut in to the work piece in successive order and each in a somewhat different placement. Each hob tooth cuts its own profile depending on the form of cutter , but the accumulation of these straight cuts creates a curved form of the gear teeth, hence the name generating process. One rotation of the task completes the cutting upto specific depth upto which hob is certainly fed unless the apparatus has a wide face.
This methodis specifically adopted to cutting large teeth which are hard to cut by formed cutter, and to cut bevel-gear teeth. It isn’t 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 correct relationship to the longitudinal motion of the cutter as if both roll with each other as a rack and pinion. Initially 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 utilization of the formed tool for finishing is certainly impracticable for the bigger pitches which are completed by an individual pointed tool. The amount 
of cuts required is dependent upon how big is the tooth, quantity of stock to be taken out, and the kind of material.