After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a brief rack cutter of a practical size to be used. Cutter is again fed back to depth and routine is repeated. Quantity of teeth is managed by the device gearing, and pitch and pressure angle by the rack cutter. This technique can be used for generation of exterior spur gears, being ideally fitted to cutting large, double helical gears. For producing helical the teeth, the cutter slides tend at the gear tooth helix angle.
The hob is fed in to the gear blank to the proper depth and both are rotated together as if in mesh. The teeth of the hob cut in to the work piece in successive purchase and each in a somewhat different placement. Each hob tooth cuts its profile depending on the form of cutter , however the accumulation of these straight cuts creates a curved form of the gear teeth, therefore the name generating procedure. One rotation of the task completes the reducing upto certain depth upto which hob can be fed unless the apparatus has a wide face.
This gear rack for Machine Tool Industry methodis specifically adopted to cutting large teeth which are challenging to cut by formed cutter, and also to cut bevel-gear teeth. It isn’t widely used at the moment.
In gear planing procedure, the cutter consists of 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 together as a rack and pinion. At first the cutter can be 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 method, both roughening and finishing cuts are taken with single pointed tools. The use of the formed tool for finishing is definitely impracticable for the larger pitches which are completed by a single pointed tool. The number of cuts required depends upon the size of the tooth, amount of stock to be eliminated, and the type of material.