The goal of a bearing is to provide relative positioning and rotational freedom while transmitting a load between two parts, commonly a shaft and its housing. The object of lubrication is to reduce the friction, wear, and heating between two surfaces moving relative to each other. This is done by inserting a substance, called lubricant, between the moving surfaces. The study of lubrication and the design of bearings are concerned mainly with phenomena related to the oil film between the moving parts. Note that tribology may be defined as the study of the lubrication, friction, and wear of moving or stationary parts. The literature on this complex subject is voluminous. Much is collected in the CRC Handbook of Lubrication, sponsored by the American Society of Lubrication Engineers [1]. Also see [2-6]. The website www.machinedesign.com includes general information on bearings and lubrication.

There are two parts in this chapter. In Part A, the fundamentals of lubrication with particular emphasis on the design of journal (so-called sleeve or sliding) bearings is discussed. The basic forms of journal bearings are simple. In Part B, concern is with rolling bearings, also known as rolling-element bearings, and antifriction bearings. We describe the most common types of rolling bearings, bearing dimensions, bearing load, and bearing life. There is also a brief discussion on materials, mounting, and lubricants of rolling bearings. Rolling-element bearings are employed to transfer the main load through elements in rolling contact, and they have been brought to their present state of perfection only after a long period of development. Either ball bearings or roller bearings, they are made by all major bearing manufacturers worldwide.