After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus enabling a brief rack cutter of a practical duration to be utilized. Cutter is once again fed back to depth and cycle is repeated. Amount of teeth is managed by the machine gearing, and pitch and pressure angle by the rack cutter. This method is utilized for generation of external spur gears, being ideally suited for cutting large, dual helical gears. For generating helical teeth, the cutter slides are inclined at the gear tooth helix angle.
The hob is fed in to the gear blank to the proper depth and both are rotated together as if in mesh. One’s teeth of the hob cut in to the function piece in successive order and each in a somewhat gear rack for Machine Tool Industry china different placement. Each hob tooth cuts its own profile based on the form of cutter , however the accumulation of these directly cuts produces a curved form of the gear teeth, therefore the name generating procedure. One rotation of the work completes the slicing upto certain depth upto which hob is definitely fed unless the gear has a wide face.
This methodis specifically adopted to cutting large teeth which are tough to cut by formed cutter, and to cut bevel-gear teeth. It isn’t widely used at present.
In gear planing procedure, 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 with each other as a rack and pinion. Initially the cutter is usually 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 method, both roughening and completing cuts are taken with single pointed tools. The utilization of the formed device for finishing is impracticable for the bigger pitches which are completed by an individual pointed tool. The amount of cuts required depends upon the size of the tooth, amount of stock to be eliminated, and the type of material.