Machine Setting for Cutting Spur Gear

The cutter mounting face and the spindle mounting face are cleaned and the cutter is then mounted on the spindle. The cutter is checked for true running. The blank is then mounted on the table. In the same manner as that for hobbing, the mounting arrangement depends whether it is one off, batch or mass roduction job. For one off and batch production, the work pieces are checked for runout. For mass production, the fixture design should ensure repetitive acceptable runout on the clamped job. The index change gears are calculated and these are fixed. The stroke of the machine is adjusted so that it travels 3 mm beyond the job width for both forward and return strokes. Total stroke is usually kept 6 mm. Longer than the job face-width. The table is moved to feed into the job by hand so that the cutter just grazes the gear blank. The machine is started with infeed kept to zero. The cutter will then mark finely the tooth traces on the outside portion of the gear blank. By counting these traces, it is confirmed that the index gears chosen are correct. In auto cycle, the table moves rapidly from its loading position to a point just before the actual start of tooth cutting. This point can be varied to suit various sizes of the gear blank and the cutter. From this point, the infeed is engaged automatically, and the table continues to infeed until full depth is reached. The table movement then stops at this point and the cutting continues for a further rotation of the blank for a value slightly larger then 360o to ensure that all the teeth are cut to correct depth. After this the table retracts to the starting position and the machine stops. Tooth thickness is measured. If it is found more than the drawing dimensions, the stop point of infeed is shifted to get more depth of cut. Once correct tooth thickness is obtained, further jobs can be cut at this setting. The cycle described here is a single pass cycle as the job is finished in one pass.

In two-pass cycle, the first infeed stops slightly before the full depth is reached thereby leaving finishing stock on the teeth. After one revolution, the finishing infeed starts and continues until full depth is reached. The job rotates further through a rotation slightly larger than 360o. After this the table retracts to the loading position and the machine stops. The job is then unloaded.