After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus enabling a short rack cutter of a practical duration to be used. Cutter is again fed back again to depth and routine is repeated. Quantity of teeth is controlled by the device gearing, and pitch and pressure position by the rack cutter. This method can be used for generation of exterior spur gears, being preferably fitted to cutting large, dual helical gears. For creating helical the teeth, the cutter slides are inclined at the apparatus tooth helix angle.
The hob is fed in to the gear blank to the proper depth and the two are rotated together as though in mesh. The teeth of the hob cut into the function piece in successive order and each in a somewhat different position. Each hob tooth cuts its own profile based on the form of cutter , however the accumulation of these directly cuts creates a curved kind of the gear teeth, thus the name generating procedure. One rotation of the work completes the trimming upto certain depth upto which hob is definitely fed unless the gear includes a wide face.
This methodis specifically adopted to cutting large teeth which are challenging to cut by formed cutter, and also to cut bevel-gear teeth. It is not widely used at present.
In gear planing process, the cutter consists of 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 together as a rack and pinion. Initially the cutter is fed into complete tooth depth with cutter reciprocating and blank stationary. Involute form is produced as the blank rotates and involute rack cutter feeds longitudinally.
In the other technique, both roughening and completing cuts are taken with gear rack for Machine Tool Industry china single pointed tools. The usage of the formed tool for finishing can be impracticable for the bigger pitches which are completed by an individual pointed tool. The number of cuts required is dependent upon the size of the tooth, quantity of share to be removed, and the type of material.