Gear-grinding

Heat-treated gears can be finished either by grinding or by lapping. This process of gear finishing is becoming obsolete these days, as the shaving process is quite satisfactory and cheaper than gear-grinding. But when the high accuracy associated with profile grinding is required, it is the only process to be used. By grinding, teeth can be finished either by generation or by forming. In the former the work is made to roll in contact with a flat faced rotating grinding wheel, which corresponds to the face of the imaginary rack meshing with the gear. One side of tooth is ground at a time. Later on the grinding wheel is given the shape as formed by space between two adjacent teeth and both flanks are finished together. The second method tends to be rather quicker, but both give equally accurate results and which of the method is to be used depends upon the availability of the type of grinding machine. The disadvantage of gear-grinding is that considerable time is consumed in the process and also the surfaces of the teeth have small scratches or ridged which increase both wear and noise. To eliminate these defects ground gears are frequently lapped.