Commonly used gear materials include quenched and tempered steel, quenched steel, carburized and quenched steel and nitrided steel. The strength of cast steel is slightly lower than that of forged steel, and it is often used for larger gears; gray cast iron has poor mechanical properties and can be used in light-load open gear transmissions; ductile cast iron can partially replace steel to make gears; plastic gears are often used In places where light load and low noise are required, the paired gears generally use steel gears with good thermal conductivity. After years of development in the gear industry, future gears are moving closer to heavy load, high speed, high precision and efficiency, and higher requirements are put forward for the size, weight, service life and cost performance of gear products.

Gear racks generally include gear teeth, tooth grooves, end faces, normal faces, addendum circles, tooth root circles, base circles, and index circles. Gear teeth are abbreviated as teeth, which are each convex part of the gear used for meshing. These convex parts are generally arranged in a radial pattern. The teeth on the mating gears are in contact with each other, so that the gears can continuously mesh and run. Cogging is the space between two adjacent gear teeth on a gear; the end surface is on a cylindrical gear or cylindrical worm, and is perpendicular to the plane of the gear or worm axis. The end surface is the plane at both ends of the gear, and the normal surface refers to the plane perpendicular to the tooth line of the gear. The tip circle refers to the circle where the top of the tooth is located, and the root circle refers to the circle where the bottom of the groove is located. The base circle forms the involute generating line as a pure rolling circle, and the index circle is the reference circle for calculating the geometrical dimensions of the gear in the end face.

Today, the manufacturing process of many gear processing plants has been developed to further study the mechanism of gear tooth damage, which is the basis for establishing a reliable strength calculation method, and is the theoretical basis for improving the bearing capacity of the gear and extending the life of the gear. The development of gears is represented by the new tooth profile of the arc tooth profile; the study of new gear materials and the new technology of manufacturing gears; the study of the elastic deformation of the gears, the manufacturing and installation errors and the distribution of temperature fields, and the modification of gear teeth to Improve the smoothness of the gear operation, and increase the contact area of ​​the gear teeth when fully loaded, thereby increasing the load-bearing capacity of the gear. Friction, lubrication theory and lubrication technology are the basic work in the research of gears. The study of elastohydrodynamic lubrication theory, the promotion of the use of synthetic lubricants and the appropriate addition of additives to the oil can not only improve the bearing capacity of the tooth surface, but also Improve transmission efficiency.