After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus enabling a brief rack cutter of a practical duration to be utilized. Cutter is once again fed back to depth and routine is repeated. Number of teeth is controlled by the device gearing, and pitch and pressure position by the rack cutter. This method can be used for generation of exterior spur gears, being preferably suited for cutting large, dual helical gears. For making helical tooth, the cutter gear rack for Machine Tool Industry china slides are inclined at the apparatus tooth helix angle.
The hob is fed into the gear blank to the correct 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 different placement. Each hob tooth cuts its profile depending on the shape of cutter , but the accumulation of these directly cuts generates a curved type of the gear teeth, therefore the name generating procedure. One rotation of the task completes the reducing upto particular depth upto which hob is usually fed unless the apparatus includes a wide face.
This methodis specially adopted to cutting large teeth which are tough to cut by formed cutter, and also to cut bevel-gear teeth. It is not widely used at present.
In gear planing process, the cutter includes true involute rack which reciprocates over the face of the blank and the blank rotates in the correct relationship to the longitudinal movement of the cutter as though both roll with each other as a rack and pinion. Initially 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 method, both roughening and finishing cuts are taken with single pointed tools. The utilization of the formed device for finishing can be impracticable for the bigger pitches which are finished by a single pointed tool. The number of cuts required is dependent upon how big is the tooth, quantity of stock to be eliminated, and the type of material.