After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a short rack cutter of a practical duration to be used. Cutter is once again fed back again to depth and routine is repeated. Amount of teeth is managed by the device gearing, and pitch and pressure position by the rack cutter. This method can be used for generation of external spur gears, being gear rack for Machine Tool Industry china ideally suited for cutting large, double 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 correct depth and both are rotated together as if in mesh. The teeth of the hob cut into the work piece in successive purchase 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 straight cuts creates a curved type of the gear teeth, hence the name generating process. One rotation of the task completes the slicing upto specific depth upto which hob is certainly fed unless the gear includes a wide face.
This methodis specifically adopted to cutting large teeth which are difficult to cut by formed cutter, and also to cut bevel-gear teeth. It isn’t widely used at present.
In gear planing procedure, the cutter includes accurate involute rack which reciprocates across the face of the blank and the blank rotates in the right relationship to the longitudinal motion of the cutter as though both roll jointly as a rack and pinion. At first the cutter is usually fed into complete tooth depth with cutter reciprocating and blank stationary. Involute shape is generated as the blank rotates and involute rack cutter feeds longitudinally.
In the other method, both roughening and completing cuts are taken with single pointed tools. The utilization 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 the size of the tooth, amount of share to be removed, and the kind of material.