Thrust bearings are utilities that allow for relative motion between objects; thrust bearings are distinct from other bearing varieties in that they are used only to bear axial loads.
In order for an object to move relative to another object with which it is in physical contact, the friction between the two objects must be overcome. Bearings are used to reduce friction between objects that are designed to constantly move relative to each other. Examples of such objects are bicycle wheels and the axels on which they are mounted and sliding drawers and the slides on which they are mounted. Different bearings come in different configurations. One of the most common bearing systems is the ball bearing system. A simple ball bearing involves several balls, which can be made of steel, ceramics or other materials, that are placed in a track called a race. The bearing is placed between two objects, and when one object must move, the balls in the track move in order to accommodate the movement of the borne object. There are many examples of systems that make use of ball bearings, and each of those different systems involves a different kind of load.
Thrust bearings are used in situations where an axial load must be borne. The simplest way to conceptualize the bearing of an axial load is to imagine a doughnut made of metal that has been cut in half lengthwise. If the bottom half of the doughnut is hollowed out, leaving only a sort of half-doughnut shell, a deep channel would remain. If ball bearings were then placed in that channel, and if the other half of the doughnut was also hollowed out and then placed on top of the ball bearings, the top half of the doughnut could spin around freely because of the near frictionless motion of the ball bearings. Any object placed on top of the upper doughnut is considered to be an axial load. Such bearings are used in spinning table-top serving dishes, barstools, remote control helicopters and in a variety of other products. Thrust bearings are among the most common bearing varieties because of the extensive number of applications in which an axial load must be borne and moved relative to another object. They are simple but important tools in a wide variety of contexts.