After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and gear rack for Machine Tool Industry china indexed back to its starting position, thus enabling a short rack cutter of a practical length to be used. Cutter is once again fed back again to depth and routine is repeated. Quantity of teeth is managed by the device gearing, and pitch and pressure position by the rack cutter. This method is used for generation of exterior spur gears, being ideally fitted to cutting large, dual helical gears. For producing 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 the two are rotated together as if in mesh. The teeth of the hob cut into the function piece in successive purchase and each in a slightly different placement. Each hob tooth cuts its profile depending on the form of cutter , but the accumulation of these directly cuts creates a curved type of the gear teeth, thus the name generating process. One rotation of the task completes the trimming upto certain depth upto which hob can be 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 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 though both roll jointly as a rack and pinion. Initially the cutter is usually 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 technique, both roughening and completing cuts are taken with single pointed tools. The usage of the formed device for finishing is certainly impracticable for the larger 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 taken out, and the type of material.