Gear Finishing Processes & Operations – What are Different Types of Gear Finishing

Gear finishing is intended to ensure the profile of gear teeth is accurate and smooth and performed through the following operations.

1. Gear Shaving

Shaving is a kind of generating manufacturing or machining method commonly used to improve the accuracy of tooth profile and reduce the roughness of tooth surface after hobbing or gear shaping. A gear shaving cutter is essentially a helical gear with high precision and cutting ability. It is meshing with the machine tool of gear blank is equivalent to the meshing of staggered shaft helical gear. It uses the relative motion speed between conjugate tooth surfaces to produce cutting motion and form generative cutting. In the process of meshing with the gear to be machined, many cutting edges on the tooth surface of the shaving cutter shave fine chips from the workpiece surface, so as to improve the tooth profile accuracy and reduce the tooth surface roughness.

2. Gear Honing

Gear honing is a method used to finish the gear after heat treatment. It is a method of cutting teeth by means of the pressure and relative sliding between the tooth surfaces during the meshing process of the honing wheel and the honed gear. In terms of kinematic relationships, honing and shaving are the same. The principle of gear honing and gear shaving is exactly the same, but when the gear hardness is higher than HRC35, the gear shaving cutter will not work. At this time, it is recommended to use gear honing instead of gear shaving. Honing has little effect on the accuracy of tooth profile.

3. Gear Lapping 

Gear lapping is one of the gear finishing operations. The principle is to mesh the grinding wheel (similar in shape to the gear, which can be external gear or internal gear) with the gear to be studied under slight braking, add abrasive between the tooth surfaces, and use its relative sliding to grind a very thin layer of metal on the tooth surface of the gear to be studied, so as to reduce the tooth surface roughness and correct the partial error of the gear. There are two kinds of gear lapping methods: parallel axis gear lapping method and staggered axis gear lapping method. It is suggested that the gear lapping method should be selected when the workpiece allowance is small, so as to effectively improve the precision and productivity of gear lapping.

4. Gear Grinding

According to the processing principle, gear grinding can be divided into forming method and generating method. Specially used for finishing hardened gears. The cutting motion of gear grinding by the generating method is similar to that of gear hobbing. It is a kind of tooth profile finishing method, especially for hardened gears, it is often the only finishing method. The generating method can be ground with a worm wheel, conical wheel, or dished wheel.

5. Hard Turning

The above four methods are mainly aimed at the finishing of gear tooth profile, so as to ensure the accuracy and roughness of tooth profile. What tools are selected for finishing the inner hole and end face of high hardness gear after heat treatment, and how to ensure its accuracy and roughness requirements? The answer is the PCBN tool. PCBN tool is an artificial cubic boron nitride tool. Its hardness is second only to the diamond tool. It is unique in the field of high hardness materials and difficult to process materials. At the same time, after decades of research and development, it has been widely used in the field of processing hard steel, cast iron, powder metallurgy, and other different materials. At present, PCBN blades of hard turning gears are mainly CNC cutters, such as DNGA series, TNGA series, VNGA series, etc. PCBN blades are often used for finishing the inner hole and end face of gears.