A gear refers to a mechanical component with teeth on the rim that can continuously mesh and transmit motion and power. The application of gears in transmission has been around for a long time. At the end of the 19th century, the principle of the gear cutting method and the emergence of specialized machine tools and cutting tools that used this principle for gear cutting emerged one after another. With the development of production, the smoothness of gear operation was valued. Tooth - Each protrusion on a gear used for meshing. Generally speaking, these protruding parts are arranged in a radial pattern. The teeth on the paired gears come into contact with each other, resulting in continuous meshing operation of the gears. Generally, there are gear teeth, tooth grooves, end faces, normal surfaces, tooth top circles, tooth root circles, base circles, and indexing circles.