After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a brief rack cutter of a practical duration to be utilized. Cutter is once again fed back again to depth and cycle 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 preferably fitted to cutting large, dual helical gears. For producing helical teeth, the cutter slides tend at the apparatus tooth helix angle.
The hob is fed in to the gear blank to the correct depth and the two are rotated together as though in mesh. The teeth of the hob cut into the work piece in successive purchase and each in a slightly different position. Each hob tooth cuts its own profile depending on the form of cutter , but the accumulation of these directly cuts generates a curved form of the gear teeth, hence the name gear rack for Machine Tool Industry china generating procedure. One rotation of the work completes the reducing upto particular depth upto which hob is definitely fed unless the apparatus includes a wide face.
This methodis specially adopted to cutting large teeth which are challenging to cut by formed cutter, and to cut bevel-gear teeth. It is not widely used at present.
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 jointly as a rack and pinion. Initially the cutter is usually fed into full tooth depth with cutter 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 utilization of the formed tool for finishing is certainly impracticable for the bigger pitches which are finished by a single pointed tool. The amount of cuts required depends upon how big is the tooth, quantity of stock to be removed, and the type of material.