After the gears are manufactured, they may still need to be finished to improve surface finish and dimensional accuracy. Gears can be done in several different ways, such as grinding or lapping.
What is gear grinding?
Gear grinding is the process of giving gear teeth a very fine finish and high precision by using a grinding tool and applying a fine-grained abrasive between the workpiece material and a closely-fitting surface called a grinding plate. By running a pair of gears together in a gear grinder, pressure is applied to feed a liquid abrasive into the gear pair, and as the gears rotate, a small amount of metal is removed to machine the tooth flanks to achieve the desired contact pattern.
Grinding generally improves the wear resistance of gear teeth and corrects small errors in involute profile, helix angle, pitch and concentricity that arise during forming, cutting or heat treating of gears. For this reason, gear grinding is most often used in hardened gear pairs where very quiet running is required. Note: Gear grinding is a mating process; two gears that have been ground and matched need to be used in pairs, and should be replaced at the same time, not one of them individually.
What is lapping?
Gears can be manufactured by direct grinding, direct cutting, or cutting and lapping to size. Typically, gear grinding is performed after the gears have been rough-shaped and heat-treated to a high hardness; for parts above 350 HB (38 HRC), where cutting becomes very difficult, grinding is usually performed, although hard flanking can also be used process. The amount of metal removed by grinding gear teeth is usually very small. Furthermore, in the case of fully hardened steel, grinding of the gear becomes the procedure of choice, where it may be difficult to keep the heat treatment deformation of the gear within acceptable limits. Finally, in a few cases, in order to save the cost of expensive cutting tools (such as hobs, gear shapers or razors), it is possible to grind medium-hard gears that can be done by cutting.
The two basic methods of gear grinding are form grinding (non-generating) and generating (worm grinding) grinding. The profile grinder uses a disc grinding wheel to grind both sides of the gear teeth. The shape of the grinding wheel is the groove shape of the gear.
Alternatively, the resulting grinding wheel has a straight edge.