Running-in: when the gear pair is assembled, the gear pair runs with certain lubricant at zero load or under the condition that the load and the speed are gradually increased, so that the uneven peaks on the surface of the engaged table can be abraded gradually, the actual contact area of the two contact surfaces can be enlarged, and thus the most proper gap between the engaged surfaces and the best economic benefit can be obtained.
Due to the advantages of high transmission efficiency, accurate transmission ratio, large power range and the like, gear mechanisms are widely applied in industrial products, and the design and manufacturing quality of the gear mechanisms directly influence the quality of industrial products. When two gears are engaged, one gear will drive the other gear to rotate to transmit power; and when the two gears are separated, the gears on the two sides can also be driven through a chain, a crawler track or a belt to transmit power.
Although the bearing capacity is low, the gear with the soft gear surface is easier to manufacture and good in running-in property and is mostly used in general machines with no strict requirements on the transmission dimensions and weight. As the burden of the small gear is larger in the paired gears, the surface hardness of the small gear is usually larger than that of the large gear so that the service live of the small gear and the large gear can be roughly the same.
The bearing capacity of the gear with the hard surface is large. The gear is precisely cut and then subjected to quenching, surface quenching or carburizing quenching so as to improve the hardness. It is inevitable that the gear is deformed in heat treatment, so grinding or lapping or finishing needs to be conducted after heat treatment to eliminate the tolerance generated by deformation and improve the precision of the gear.