After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a short rack cutter of a practical length to be used. Cutter is once again fed back again to depth and cycle is repeated. Amount of teeth is controlled by the machine gearing, and pitch and pressure position by the rack cutter. This method is utilized for generation of exterior spur gears, being ideally suited for cutting large, dual helical gears. For making helical teeth, the cutter slides tend at the gear tooth helix angle.
The hob is fed into the gear blank to the correct depth and the two are rotated together as if in mesh. One’s teeth of the hob cut into the function piece in successive order and each in a slightly different placement. Each hob tooth cuts its own profile based on the shape of cutter , however the accumulation of these directly cuts produces a curved type of the gear teeth, thus the name generating procedure. One rotation of the task completes the cutting upto particular depth upto which hob can be fed unless the gear includes a wide face.
This methodis specifically adopted to cutting large teeth which are tough 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 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 form 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 utilization of the formed tool for gear rack for Machine Tool Industry china finishing can be impracticable for the larger pitches which are completed by a single pointed tool. The amount of cuts required depends upon the size of the tooth, quantity of share to be eliminated, and the type of material.