The lubricant forms an oil film between the sliding and rolling surfaces of the bearing, preventing metal friction even under heavy loads. Rolling bearings are generally lubricated with oil or grease, and in some special cases solid lubricants are used.

　　Lubricants reduce friction, it also prevents wear and corrosion, and prevents contamination of bearings by solids and liquids. Theoretically, a well lubricated bearing should last forever under ideal working conditions. Of course, it is not possible in practice, but if the bearing can be lubricated correctly, the bearing will achieve a long working life. The usage of grease and bearing grease is different, so how should grease and bearing grease be selected?

　　1. Grease and grease are general-purpose rolling bearing lubricants. Grease refers to a semi-fluid to solid thickener substance mixed in a liquid (base oil). About 90 percent of the mixture is mineral or synthetic oil and thickener, and the metal soap is a compound of a metal hydroxide and a fatty acid, such as lithium soap. Using different soaps, base oils and additives, greases suitable for various applications can be created.

　　2. The ability to produce a film The main factors that determine the thickness of the oil film are rotational speed, temperature and viscosity. Another factor in selecting the thickness of the oil film is the requirement for the service life of the bearing. The three important lubrication conditions are: boundary lubrication, hydrodynamic lubrication and elastic hydrodynamic lubrication.

　　3. How does the grease work in the bearing? The thickener is composed of reticulated soap fibers, which function like a container for lubricating oil. The spaces of the mesh are filled with lubricating oil, just as the pores in a sponge are filled with water. If a wet sponge is squeezed, the water will flow out, and the grease will be like a sponge, and the oil will be discharged due to being squeezed, but the grease in the bearing is rarely directly squeezed and discharged, because a newly lubricated bearing is running in When the grease is active in the inner space of the bearing.

　　For example, in bearings used under vibration, if the grease used is not mechanically stable enough, it will be continuously vibrated into or thrown out of the bearing, which will cause the structure of the metal soap to collapse and destroy the grease.

　　The main reason for the grease to drain to the sliding surface is not all mechanical movement, but the temperature rise of the grease around the bearing. Sufficient oil reaches the sliding surfaces, and the selected grease has properties suitable for the type of bearing and operating conditions. Some special requirements.