After completion of 1 or two teeth, the blank and cutter stop feeding and the cutter is withdrawn and indexed back again to its starting position, thus enabling a short rack cutter of a practical length to be utilized. Cutter is again fed back again to depth and routine is repeated. Quantity of teeth is controlled by the machine gearing, and pitch and pressure angle by the rack cutter. This method can be used for generation of external spur gears, being ideally suited for cutting large, dual helical gears. For creating helical teeth, 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 both are rotated together as if in mesh. One’s teeth of the hob cut in to the function piece in successive purchase and each in a slightly different position. Each hob tooth cuts its profile based on the shape of cutter , however the accumulation of these directly cuts produces a curved kind of the gear teeth, therefore the name generating procedure. One rotation of the task completes the slicing upto specific depth upto which hob is usually fed unless the gear includes a wide face.
This methodis specifically adopted to cutting large teeth which are tough to cut by formed cutter, and to cut bevel-gear teeth. It isn’t widely used at the moment.
In gear planing gear rack for Machine Tool Industry process, the cutter consists of accurate involute rack which reciprocates over the face of the blank and the blank rotates in the correct relationship to the longitudinal motion of the cutter as if both roll collectively as a rack and pinion. Initially the cutter is definitely fed into full tooth depth with cutter reciprocating and blank stationary. Involute form 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 utilization of the formed tool for finishing is usually impracticable for the bigger pitches which are finished by a single pointed tool. The amount of cuts required depends upon how big is the tooth, amount of share to be taken out, and the type of material.