After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus allowing a brief rack cutter of a practical size to be utilized. Cutter is again fed back again to depth and routine is repeated. Amount of teeth is controlled by the machine gearing, and pitch and pressure position by the rack cutter. This technique is utilized for generation of exterior spur gears, being ideally fitted to cutting large, dual helical gears. For producing helical tooth, the cutter slides are inclined at the apparatus tooth helix angle.
The hob is fed in to the gear blank to the correct 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 position. Each hob tooth cuts its own profile depending on the shape of cutter , but the accumulation of these straight cuts creates a curved form of the gear teeth, therefore the name generating procedure. One rotation of the task completes the cutting upto certain depth upto which hob is usually fed unless the gear gear rack for Machine Tool Industry china includes a wide face.
This methodis specially adopted to cutting large teeth which are difficult to cut by formed cutter, and to cut bevel-gear teeth. It is not widely used at the moment.
In gear planing process, the cutter includes 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 though both roll jointly as a rack and pinion. Initially the cutter can be fed into full 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 finishing cuts are taken with single pointed tools. The usage of the formed tool for finishing can be impracticable for the larger pitches which are completed by an individual pointed tool. The amount of cuts required depends upon how big is the tooth, amount of share to be removed, and the kind of material.