After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus enabling a brief rack cutter of a practical duration to be utilized. Cutter is again fed back again to depth and routine is repeated. Number of teeth is controlled by the machine gearing, and pitch and pressure position by the rack cutter. This method is used for generation of exterior spur gears, being ideally suited for cutting large, double 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 the two are rotated together as though in mesh. One’s teeth of the hob cut into the function piece in successive purchase and each in a slightly different placement. Each hob tooth cuts its own profile based on the form of cutter , but the accumulation of these straight cuts produces a curved form of the gear teeth, therefore the name generating process. One gear rack for Machine Tool Industry china rotation of the task completes the cutting upto particular depth upto which hob can be fed unless the apparatus includes a wide face.
This methodis specially adopted to cutting large teeth which are difficult to cut by formed cutter, and also to cut bevel-gear teeth. It is not widely used at the moment.
In gear planing procedure, the cutter contains accurate involute rack which reciprocates over the face of the blank and the blank rotates in the right relationship to the longitudinal movement of the cutter as if both roll together as a rack and pinion. Initially the cutter is definitely fed into complete 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 device for finishing can be impracticable for the larger pitches which are completed 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 kind of material.