A Bearing is a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts.
The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Many bearings also facilitate the desired motion as much as possible, such as by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads applied to the parts. Common motions permitted by bearings are namely axial rotation, linear motion, spherical rotation and hinge motion. Types of bearings include magnetic bearings, rolling element bearings, fluid bearings, plain bearings, flexure bearings etc. One of the purposes of bearings is to reduce friction, most often on a rotating shaft. It may be made of different materials including sintered bronze, which holds oil to reduce friction, and various metals which are cast in place to make a soft slippery surface for really heavy shafts. |
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