After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a brief rack cutter of a practical size to be utilized. Cutter is once again fed back to depth and cycle is repeated. Quantity of teeth is managed by the machine gearing, and pitch and pressure angle by the rack cutter. This technique is utilized for generation of exterior spur gears, being ideally fitted to cutting large, dual helical gears. For producing helical teeth, the cutter slides tend at the gear 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. One’s teeth of the hob cut in to the function piece in successive order and each in a slightly different placement. Each hob tooth cuts its own profile depending on the form of cutter , but the accumulation of these directly cuts produces a curved type of the gear teeth, hence the name generating procedure. 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 challenging to cut by formed cutter, and to cut bevel-gear teeth. It is not widely used at present.
In gear planing process, the cutter consists of true involute rack which reciprocates over the face of the blank and the blank rotates in the right relationship to the longitudinal motion of the cutter as if both roll jointly as a rack and pinion. At first the cutter is certainly 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 technique, both roughening and completing cuts are taken with single pointed tools. The usage of the formed device for finishing can be impracticable for the bigger pitches which are completed by a single pointed tool. The amount of cuts required depends upon the size of the tooth, amount of share to be taken out, and the type of gear rack for Machine Tool Industry china material.