Bearing Terms

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A.B.E.C.
Annular Bearing Engineering Committee. Used as prefix for tolerance grades of bearings as set up by this committee.

ABMA
American Bearing Manufacturers Association, a standards organization that deals with all aspects of bearing technology.

Adapter Sleeve
Axially slotted sleeve with cylindrical bore, tapered outside surface and male screw thread at small end used with locknut and lockwasher for mounting of bearings with tapered bore on cylindrical outside surface of shaft. Also called pull-type sleeve.

AISI
American Iron and Steel Institute, an association of North American steel producers that establishes standards for steel materials.

Annealing
A type of heat treatment, typically used to soften a material, which involves heating a material to a specific temperature, holding it at that temperature for a specific period of time, then cooling slowly to room temperature.

Anodizing
An electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. Anodizing increases corrosion resistance and wear resistance.

Anti-friction Bearing
Commonly used term for rolling element bearing.

Anti-Rotation Pin
A small rivet head on the OD of a bearing insert used to help keep the outer bearing ring from spinning in a bearing housing.

Axial Internal Clearance
In a ball or roller bearing assembly, the total maximum possible movement parallel to bearing axis of inner ring in relation to outer ring.

Axial Load
A load exerted parallel to the shaft that a bearing is mounted on, also known as a thrust load.

Ball Bearing
A type of rolling-element bearing which uses balls to maintain the separation between the moving parts of the bearing.

Ball Complement
Number of balls used in a ball bearing.

Basic Dynamic Load Rating
The calculated constant applied load which a group of identical bearings with stationary outer rings can theoretically endure for a rating life of 1 million revolutions of inner ring.

Basic Static Load Rating
The maximum applied load a bearing can endure without excessive permanent deformation.

Bearing
A mechanical device used to reduce friction and guide motion of two or more parts which articulate in differing directions.

Bore
The smallest internal dimension of a cylindrical object, typically referring to the inside diameter of the inner bearing ring.

Brinelling
The indentation of an inner or outer raceway ring caused by the rolling elements. There are two types; True Brinelling is due to material deformation under excessive operating pressure and False Brinelling is vibration related.

Cage
A device used to separate the rolling elements of a bearing and help guide the rolling elements along their intended pathway (also known as a retainer).

Carburizing
A heat treating method that enables the surface layer of a material to be harder than its inner core.

Casting
A process by which a material is introduced into a mold while liquid, and allowed to solidify into a specific shape.

Concentric
Circles or diameters that have the same exact center.

Corrosion
A chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties.

Dynamic Load
A load exerted on a bearing in motion.

Eccentric
Circles or diameters not having the same exact centers.

Elastohydrodynamic Lubrication
A film of oil between two mating surfaces which gives the best protection against wear, where oil flows and creates a hydraulic pressure between the two surfaces, under perfect conditions this type of lubrication will not allow wear.

End Play
The axial play of the outer ring in a bearing. The measured maximum possible movement parallel to bearing axis of the inner ring in relation to outer ring.

Extended Inner Ring
The inner bearing ring is extended on one or both sides of the raceway to improve guidance of the shaft and to permit fixing of a locking device and/or to provide space for sealing devices.

External Race
The ball path on an inner ring.

Fit
The amount of internal clearance in a bearing. Fit can also be used to describe shaft and housing size and how they relate to the bore or outside diameter.

Fixed Bearing
Bearing which positions shaft against axial movement in both directions.

Floating Bearing
Bearing designed or mounted so as to permit axial displacement between shaft and housing.

Hardening
A process of heating parts to a high temperature and then quenching in oil, water, air, or solution to increase the hardness and wear resistance.

Heat Treatment
A combination of heating and cooling operations applied to a metal or alloy to obtain desired microstructure conditions or properties.

Housing
A rigid structure that supports and locates the seal assembly with respect to the shaft.

Housing Fit
Amount of interference or clearance between bearing outside surface and housing bearing seat.

Inner Ring
The inner part of a bearing that fits on a shaft and contains the external raceway for the rolling elements. Sometimes the shaft is stationary and the housing rotates.

Insert
The generic term for a bearing with a spherical outside surface and an extended inner ring with a locking device, which is used in a mounted assembly, such as a pillow block or flange unit.

Internal Clearance
Also known as fit or radial clearance, it is the distance between the rolling elements and the bearing races.

Internal Race
The ball or roller path on the bore of the outer ring. Outer Ring Raceway. Outer Raceway.

ISO
International Standards Organization, a nongovernmental worldwide federation of standards bodies from more than 140 countries to promote standardization of goods and services.

JIS
Japanese Industrial Standard, a standards organization for goods and services from Japan.

Life
“Life” of individual rolling bearing is the number of revolutions (or hours at some given constant speed) which bearing runs before first evidence of fatigue develops in the material of either ring or washer or any of rolling elements.

Loading Slot
Two crescent shaped cut out sections, typically on the back side of a bearing housing, used when assembling a bearing insert into a housing.

Locking Collar
Ring fitting over extended inner ring of insert bearing and having some physical feature to hold the bearing on a shaft.

Locknut
A nut used in combination with a lockwasher to hold a bearing in place on a shaft.

Lockwasher
A washer with tongue and prongs to hold a locknut in place.

Loose Fit
A fit or fit up of inner ring, balls, and outer ring which results in the existence of appreciable radial clearance. Can also refer to the tolerance range of a housing bore that will allow a bearing insert to align and move freely in relation to the housing.

Lubricant
A bearing lubricant lubricates the rolling and moving surfaces, protects from corrosion, conducts and transfers heat evenly, and inhibits contamination.

Lubrication Groove
A machined groove in the bore of a bearing housing or on the OD of the outer bearing ring to convey lubricant to the bearing.

Misalignment
Lack of parallelism between axis of rotating member and stationary member.

Molded Type Ball Cage
A type of molded nylon cage in which there is a single piece that is open on one face and snaps around the rolling elements after the balls have been assembled in the rings.

O.D.
The outside diameter of the outer bearing ring.

Open Bearing
A bearing without seals, shields, or slingers.

Outer Ring
The outer part of a bearing that fits into the housing and contains the internal raceway for the rolling elements.

Oxidation
This occurs when oxygen attacks petroleum fluids. The process is accelerated by heat, light, metal catalysts and the presence of water, acids, or solid contaminants. It leads to increased viscosity and deposit formation.

Precision Class
The degree of precision or accuracy to which a bearing is made.

Prelubricated Bearing
A shielded, sealed, or open bearing originally lubricated by the manufacturer.

Raceway
The ball or roller path; cut in the inner and outer ring in which the balls or rollers ride, essentially the rolling track.

Raceway Diameter
Inner Ring – the outer dimension across the diameter from raceway bottom to raceway bottom.
Outer Ring – the inner dimension across the diameter from raceway bottom to raceway bottom.

Radial Clearance
The available free space in between the rolling elements and raceways of a bearing.

Radial Load
A load exerted perpendicular to the shaft that a bearing is mounted on.

Rating Life
L10 of group of apparently identical bearings is the life in millions of revolutions that 90% of the group will complete or exceed.

Riveted Type Ball Cage
A type of stamped steel cage in which the two halves are riveted together around the balls after the balls have been assembled in the rings.

Rolling Bearing
A bearing operating with rolling rather than sliding motion between the parts supporting the load and moving in relation to each other, which comprises raceway and rolling elements. A given bearing type may be designed to support radial, axial, or combined radial and axial loads.

Runout
Displacement of surface of bearing relative to fixed point when one raceway is rotated with respect to other raceway.

Seal
A soft synthetic rubber washer with a steel core fixed in the outer ring (in the seal groove) in contact with the inner ring to retain lubricant and keep out contamination.

Shaft Fit
Amount of interference or clearance between bearing inside diameter and shaft bearing seat outside diameter.

Single Row
Bearing with one row of rolling elements.

Slinger
A component part of a bearing that is attached to the inner bearing ring and by centrifugal action, helps to protect the bearing against the ingress of foreign substances.

Snap Ring
A removable ring used to axially position a bearing or outer ring in a housing. Also used as a means of fastening a shield or seal in a bearing.

Spalling
Chipping, fragmentation, or separation of a surface coating. This is a common cause of bearing failure due to contamination, impact, or overloading.

Standard Bearing
Bearing which conforms to the basic plan for boundary dimensions of metric or inch dimensions.

Static Load
A load exerted on a bearing not in motion.

Tensile Strength
A measurement of the maximum load per unit of original area that a material has prior to fracture.

Tolerance
The amount a given dimension may vary from a nominal value. The difference between the upper and lower limits of a dimension or a specification.

Torque
The turning force acting on a rotating object, such as a shaft.

Wide Inner Ring Bearing
Bearing with inner ring extended on one or both sides in order to achieve greater shaft support and permit addition of locking device and provide additional space for sealing devices.