After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a short rack cutter of a practical length to be used. 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 angle by the rack cutter. This technique is used for generation of exterior spur gears, being ideally suited for cutting large, double helical gears. For creating helical tooth, the cutter slides tend at the gear tooth helix angle.
The hob is fed in to the gear blank to the correct depth and both are rotated together as if in mesh. The teeth of the hob cut into the function piece in gear rack for Machine Tool Industry china successive purchase and each in a slightly different position. Each hob tooth cuts its own profile based on the form of cutter , but the accumulation of these directly cuts produces a curved form of the gear teeth, hence the name generating process. One rotation of the task completes the slicing upto particular depth upto which hob can be 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 present.
In gear planing process, the cutter consists of accurate involute rack which reciprocates across the face of the blank and the blank rotates in the right relationship to the longitudinal motion of the cutter as if both roll together as a rack and pinion. Initially the cutter is fed into full 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 use of the formed device for finishing is impracticable for the larger pitches which are completed by an individual pointed tool. The amount of cuts required is dependent upon how big is the tooth, quantity of share to be removed, and the type of material.