bearings

Bearings are machine components that permit restrained relative motion between two parts while reducing friction. They support loads, guide motion, and transmit torque in rotating or oscillating systems. A bearing typically consists of an inner race and outer race, rolling elements (such as balls or rollers), and a cage to space the elements. Bearings can be classified as rolling bearings, plain bearings, and fluid or magnetic bearings.

Rolling bearings use rolling elements to convert sliding contact into discrete rolling contact, lowering friction. Plain bearings, also called sleeve or bushing bearings, rely on sliding contact in a lubricated interface. Fluid bearings support motion with a fluid film, while magnetic bearings support non-contact motion using magnetic forces.

Rolling bearings are subdivided into ball bearings and roller bearings. Ball bearings handle moderate radial and axial loads with relatively high speeds. Roller bearings carry higher radial loads and come in cylindrical, spherical, tapered, and needle variants. Thrust bearings are designed to carry axial loads, and combinations of radial and thrust bearings accommodate both load types. Materials include high-grade steel, ceramic, and engineered polymers for cages and liners.

Performance is described by static and dynamic load ratings, limiting speeds, stiffness, and life. Proper lubrication (grease or oil), seals, and lubrication management extend life. Clearance, preload, and mounting accuracy influence performance and accuracy.

Bearings are used in a wide range of applications, including automotive wheels, transmissions, industrial machinery, aerospace devices, and consumer electronics. Standards from ISO, ABMA, and JIS define dimensions, tolerances, and load ratings to support interchangeability and reliability.