After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus enabling a brief rack cutter of a practical duration to be utilized. Cutter is once again fed back to depth and cycle is repeated. Amount of teeth is managed by the device gearing, and pitch and pressure angle by the rack cutter. This method is utilized for generation of exterior spur gears, being ideally fitted to cutting large, dual helical gears. For making helical the teeth, the cutter slides are inclined at the gear tooth helix angle.
The hob is fed into the gear blank to the proper depth and both are rotated together as if in mesh. The 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 creates a curved kind of the gear teeth, thus the name generating process. One rotation of the task completes the trimming 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 hard to cut by formed cutter, and to cut bevel-gear teeth. It is not widely used at the moment.
In gear planing procedure, the cutter includes accurate 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 collectively as a rack and pinion. Initially the cutter is fed into complete tooth depth with cutter gear rack for Machine Tool Industry china reciprocating and blank stationary. Involute form is generated as the blank rotates and involute rack cutter feeds longitudinally.
In the other technique, both roughening and finishing cuts are taken with single pointed tools. The usage of the formed device for finishing can be impracticable for the bigger pitches which are finished by an individual pointed tool. The amount of cuts required is dependent upon how big is the tooth, amount of stock to be taken out, and the type of material.