After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a short rack cutter of a practical length to be utilized. Cutter is once again fed back again to depth and cycle is repeated. Amount of teeth is managed by the device gearing, and pitch and pressure angle by the rack cutter. This technique is utilized for generation of exterior spur gears, being preferably suited for cutting large, dual helical gears. For generating helical the teeth, the cutter slides are gear rack for Machine Tool Industry china inclined 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 work piece in successive order and each in a slightly different placement. Each hob tooth cuts its profile depending on the shape of cutter , however the accumulation of these straight cuts generates a curved kind of the gear teeth, hence the name generating procedure. One rotation of the work completes the cutting upto certain depth upto which hob is certainly fed unless the gear has a wide face.
This methodis specially adopted to cutting large teeth which are hard to cut by formed cutter, and to cut bevel-gear teeth. It isn’t widely used at the moment.
In gear planing process, 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 movement of the cutter as though both roll together as a rack and pinion. At first the cutter is certainly fed into complete tooth depth with cutter reciprocating and blank stationary. Involute shape 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 finishing is usually impracticable for the larger pitches which are finished by a single pointed tool. The amount of cuts required depends upon the size of the tooth, quantity of stock to be taken out, and the kind of material.