After completion of one or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus allowing a short rack cutter of a practical gear rack for Machine Tool Industry china duration to be utilized. Cutter is once again fed back to depth and cycle is repeated. Amount of teeth is managed by the device gearing, and pitch and pressure angle by the rack cutter. This method is used for generation of external spur gears, being ideally fitted to cutting large, double helical gears. For producing helical tooth, the cutter slides are inclined at the gear tooth helix angle.
The hob is fed into the gear blank to the proper depth and the two are rotated together as if 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 directly cuts produces a curved form of the gear teeth, hence the name generating procedure. One rotation of the work completes the slicing upto specific depth upto which hob is definitely fed unless the apparatus has a wide face.
This methodis specially adopted to cutting large teeth which are challenging to cut by formed cutter, and to cut bevel-gear teeth. It isn’t widely used at present.
In gear planing procedure, the cutter includes accurate involute rack which reciprocates across the face of the blank and the blank rotates in the correct relationship to the longitudinal motion of the cutter as if both roll jointly as a rack and pinion. Initially the cutter is usually 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 completing cuts are taken with single pointed tools. The use of the formed device for finishing is definitely impracticable for the bigger pitches which are finished by an individual pointed tool. The amount of cuts required is dependent upon how big is the tooth, amount of stock to be eliminated, and the kind of material.