After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a short rack cutter of a practical duration to be utilized. Cutter is once again fed back again to depth and routine is repeated. Amount of teeth is managed by the machine gearing, and pitch and pressure position by the rack cutter. This method is used for generation of external spur gears, being ideally fitted to cutting large, dual helical gears. For producing helical 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 if in mesh. The teeth of the hob cut in to the function piece in successive order and each in a slightly different placement. Each hob tooth cuts its profile based on the shape of cutter , however the accumulation of these directly cuts creates a curved type of the gear teeth, hence the name generating procedure. One rotation of the task completes the reducing upto certain depth upto which hob is certainly fed unless the gear includes a wide face.
This methodis specially adopted to cutting large teeth which are hard 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 contains 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 though both roll together as a rack and pinion. Initially the cutter is certainly fed into full tooth depth with cutter reciprocating and blank stationary. Involute form is generated as the blank rotates and involute rack cutter feeds longitudinally.
In the other method, both roughening and finishing cuts are taken with gear rack for Machine Tool Industry china single pointed tools. The use of the formed tool for finishing can be impracticable for the larger pitches which are finished by a single pointed tool. The amount of cuts required is dependent upon the size of the tooth, quantity of share to be taken out, and the type of material.