After completion of one or two teeth, the blank and gear rack for Machine Tool Industry cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a brief rack cutter of a practical duration to be utilized. Cutter is again fed back again to depth and cycle is repeated. Quantity of teeth is managed by the device gearing, and pitch and pressure angle by the rack cutter. This method is used for generation of external spur gears, being ideally suited for cutting large, double helical gears. For making helical teeth, the cutter slides tend 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 purchase and each in a slightly different position. Each hob tooth cuts its own profile based on the shape of cutter , but the accumulation of these straight cuts creates a curved form of the gear teeth, therefore the name generating process. One rotation of the task completes the trimming upto specific depth upto which hob can be 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 to cut bevel-gear teeth. It is not widely used at the moment.
In gear planing procedure, 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 jointly as a rack and pinion. At first the cutter is fed into full 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 technique, both roughening and completing cuts are taken with single pointed tools. The usage of the formed tool for finishing is usually impracticable for the bigger pitches which are completed by a single pointed tool. The amount of cuts required is dependent upon the size of the tooth, quantity of share to be eliminated, and the kind of material.