Reducer gears can be classified according to tooth type, reducer gear shape, tooth line shape, the surface on which the reducer gear is located, and the manufacturing method.

The tooth profile of the reducer gear includes the reducer gear curve, pressure angle, tooth height, and displacement. Involute gear reducer gears are easier to manufacture, so in modern gear reducer gears, involute gear reducer gears account for the majority, while cycloidal gear reducer gears and arc gear reducer gears are rarely used.

In terms of pressure angle, the bearing capacity of small pressure angle reducer gears is small; Although the bearing capacity of the high pressure angle reducer gear is high, the load of the bearing increases under the same transmission distance, so it is only used in special cases. The tooth height of the reducer gear has been standardized, and the standard tooth height is generally used. The modified reducer gear has many advantages in various mechanical equipment.

In addition, reducer gears can also be divided into cylindrical reducer gears, reducer gear shafts, non circular reducer gears, racks, worm gears, straight reducer gears, helical reducer gears, herringbone reducer gears, curved reducer gears, external reducer gears, internal reducer gears, forged reducer gears, cutting reducer gears, rolling reducer gears, calcined reducer gears, and so on.

The manufacturing materials and heat treatment process of the reducer gear have a significant impact on the bearing capacity and specification weight of the reducer gear. Prior to the 1950s, gear wheels for speed reducers were mostly made of carbon steel, changed to alloy steel in the 1960s, and mostly made of surface hardened steel in the 1970s. According to the hardness, the tooth surface can be divided into soft tooth surface and hard tooth surface.

The gear of the soft tooth surface reducer has low bearing capacity, but it is easy to manufacture and has strong running-in performance. It is mainly used for transmission without strict restrictions on size and weight, and generally manufactured with a small amount of machinery. Due to the heavy burden of matching the small wheels in the reducer gears, in order to ensure that the working life of the large and small reducer gears is approximately the same, the hardness of the tooth surface of the small wheels is generally higher than that of the large wheels.

The high bearing capacity of hard reducer gears refers to quenching, induction hardening, or carburizing quenching to improve hardness. However, during heat treatment, the reducer gear inevitably deforms, so cutting and grinding must be carried out after heat treatment to eliminate deviations caused by deformation and improve the accuracy of the reducer gear.