What is the purpose of a bearing

Update: 16-06-2020

A “bearing” may be any feature of a device that support […]

A “bearing” may be any feature of a device that supports and/or restricts degrees of freedom (movement and forces in any specific direction) of another device feature that is loaded with force that may be dynamic or static. Bearings may conform to a circle or cylinder, a flat or a contoured surface. Bearings generally are expected to reduce friction and heat and provide for efficient, smooth and quiet operation and may be designed to dampen vibration.

A bearing surface may be integral to the structure that contains the bearing feature or the bearing may be a separate element. Whether or not the bearing feature is integral or a separate element, it must withstand the stress and strain of the static (at rest) and dynamic (sliding and vibration) forces as well as withstanding the ambient operating temperature range and the heat caused by friction, and be metallurgically /chemically compatible (anti-galling/galvanically non-corrosive and chemically non-corrosive). A bearing must be reliable and function satisfactory for the desired life of the product or be economically serviced and replaced by a bearing element with a desired service life expectancy. Bearings may be required to operate with or without lubricants, and lubricants may be dry in solid or powder form (teflon, graphite, molybdenum disulfide, etc.) or liquid (water/water emulsions, hydrocarbon oils & greases, solvents, chemicals, etc.) and may even be the environment the that equipment/product operates in ( gasoline, corn syrup, etc.).

A separate bearing element may solve the issues presented by the above requirements. It may allow the structure containing the bearing to be made from a more economical material that does not have to satisfy all the requirements of a bearing. Exotic materials may be required for bearings that operate under extreme conditions. Different styles of bearings have distinctive operating characteristics.

Basic styles are flat and cylindrical sleeve bearings (plain, composite, shouldered,grooved, lubricant impregnated); roller or ball (cylindrical rollers or needles, tapered rollers, and spherical balls, single row and multiple row).

Just because a product does not have individual bearing elements does not mean the the product is a bad value. Many other factors have to be considered.