Plain bearings are used primarily in machinery that has a rotating or a sliding shaft component. Also called a journal bearing, sleeve bearings, or sliding bearings, plain bearings have no rolling elements. Some are made of relatively soft metal, such as Babbit, to protect the shaft journals. They are made of other materials as well, depending on the application and load requirements. Other bushings may be used for alignment jigs in drilling operations.
Many applications require spherical bearings that are suitable for oscillating movements and that can accommodate misalignment. Rolling bearings only partly fulfil these requirements as they are generally designed for continuous rotation and can only accommodate limited misalignment.