After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a brief rack cutter of a practical length to be utilized.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 angle by the rack cutter. This technique is used for generation of external spur gears, being preferably suited for cutting large, dual helical gears. For generating helical tooth, the cutter slides are inclined at the apparatus tooth helix angle.
The hob is fed in to the gear blank to the correct depth and both are rotated together as though in mesh. The teeth of the hob cut in to the work piece in successive order and each in a gear rack for Machine Tool Industry china slightly different position. Each hob tooth cuts its profile based on the shape of cutter , but the accumulation of these straight cuts creates a curved type of the gear teeth, thus the name generating process. One rotation of the task completes the cutting upto certain depth upto which hob is definitely 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 isn’t widely used at the moment.
In gear planing process, the cutter contains 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 if both roll collectively as a rack and pinion. At first the cutter is 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 method, both roughening and completing cuts are taken with single pointed tools. The usage 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 is dependent upon how big is the tooth, quantity of stock to be eliminated, and the type of material.