gear rack for Machine Tool Industry

After completion of one or two teeth, the blank and gear rack for Machine Tool Industry cutter stop feeding and the cutter is withdrawn and indexed back to its starting position, thus enabling a brief rack cutter of a practical size to be used. Cutter is again fed back again to depth and cycle is repeated. Amount of teeth is controlled by the machine gearing, and pitch and pressure position by the rack cutter. This method is used for generation of external spur gears, being preferably suited for cutting large, double helical gears. For producing helical tooth, the cutter 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 though in mesh. The teeth of the hob cut into the work piece in successive purchase and each in a somewhat different position. Each hob tooth cuts its own profile depending on the form of cutter , but the accumulation of these straight cuts creates a curved form of the gear teeth, thus the name generating procedure. One rotation of the work completes the slicing upto particular depth upto which hob is definitely fed unless the apparatus has a wide face.

This methodis specifically 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 contains true involute rack which reciprocates across the face of the blank and the blank rotates in the right relationship to the longitudinal movement of the cutter as if both roll collectively as a rack and pinion. Initially the cutter can be 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 technique, both roughening and completing cuts are taken with single pointed tools. The usage of the formed tool for finishing can be impracticable for the larger pitches which are finished 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.


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