Plain bearings provide low-friction sliding contact for relative motion between parts of a machine. They are the simplest type of bearing, with no rolling elements, and there are three basic types of plain bearings: radial plain bearings (also called sleeve bearings or bushings) to support rotating or reciprocating shafts, thrust bearings (also called washers) to support axial loads on shafts, and linear bearings to support and guide the motion of parts in a straight line. Flanged sleeve bearings have a flange on one end to support axial loads. Spherical plain bearings are radial bearings that allow for angular misalignment of the shaft. Plain bearings are made from durable, low-friction materials such as sintered or cast bronze alloys, plastic, or a combination of a metal shell and a plastic bearing surface. They can be lubricated externally or by a lubricant embedded in the bearing material. Plain bearings are used in automobiles, construction and mining equipment, textile manufacturing equipment, and robotics, among others.

TB Wood's manufactures bushings, pulleys, couplings, and electronic motor controls. The company, founded in 1857 and headquartered in Chambersburg, PA, meets International Organization for Standardization (ISO) standard 9001:2008.