| ABEC
The Annular Bearing Engineering
Committee.
Abrasion
The wearing, grinding, or rubbing
away by friction. Abrasion is usually due to the presence
of foreign matter such as dirt, grit or metallic particles
in the lubricant.
Acid Embrittlement
A form of hydrogen embrittlement
that may be induced in some metals by acid.
Age Hardening
Material hardening by aging. Usually
used after rapid cooling or cold working.
Aging
Any change in the properties of
a material that occurs at ambient or moderately elevated
temperatures after hot working or heat treatment. Aging
does not involve any change in the chemical composition
of the metal or alloy.
Air Bearing
Air cushion devices that are used
to "float" heavy loads on a thin film of air.
AISI
American Iron and Steel Institute,
a standards organization.
AISI Steel Identification
System
See SAE Steel Identification System.
Annealing
A type of heat treatment that
is used to soften a material. Annealing involves heating
material to a specific temperature, holding it at that
temperature for a known length of time, then cooling
slowly to room temperature.
Annulus
In a rolling element bearing,
the space between the inner and outer raceways.
Anodizing
Usually associated with aluminum,
anodizing uses anodic oxidation to form a protective
conversion coating on a metal surface.
ANSI
American National Standards Institute,
a standards organization.
Anti-Friction Bearing
An anti-friction bearing is a
bearing utilizing rolling elements between the stationary
and rotating assemblies.
ASME
American Society of Mechanical
Engineers
ASTM
American Society for Testing and
Materials
Axial Movement
The amount a bearing's inner race
is able to move perpendicular to the outer race and
perpendicular to the direction of rotation.
Ball Bearing
A class of bearing in which the
moving surface is separated from the stationary surface
by elements in the form of balls. There are three general
types of ball bearings: radial, thrust, and angular
contact.
Bearing
An object that supports weight
and reduces friction by allowing a surface to rotate
or slide when under load.
Bearing Life
Rating life, L10 (Bl0), is the
life in hours or revolutions in which 90% of the bearings
selected will obtain or exceed. Median life (average
life), L50(B50)
Brinell Hardness Number
The measure of a material's resistance
to indentation from a standard hard steel ball, normally
10mm diameter.
Brinelling
Denting caused by impact of one
bearing component against another while stationary.
Brinelling - True
The indentation of inner or outer
race material caused by the rolling elements. True brinelling
is the indentation of a part and the movement of material
due to excessive operating pressure, impact, dropping
or hammering. True brinelling is a material deformation
issue where the inner or outer race material has been
pushed or squashed out of place.
Brinelling - False
The indentation of inner or outer
race material caused by the rolling elements. False
brinelling is the indentation of a part where the indented
material has been worn away. False brinelling is a wear
issue due to metal-to-metal contact and is most often
caused by external vibration.
Cage
The device used to space, separate
and retain the balls or rollers of a rolling element
bearing. Cages are most often constructed from steel,
plastic or brass. Also referred to as a retainer.
Case Depth
The cross-sectional depth in a
material to which a hardness of Rc 58 (58 on the Rockwell
C Scale) is maintained.
Case Hardening
Hardening a material, specified
to a specific cross-sectional depth. The most common
hardening processes used are carburizing, cyaniding,
nitrifying and carbonitriding. Usually these specific
terms
The property of a material that
determines its capacity for plastic deformation without
fracturing. Ductility is most often measured by performing
a tensile test and measuring the elongation or reduction
of an area.
Dynamic
Operating Capacity
A reference standard also known
as Load Rating. The standard definition of dynamic operating
capacity is: the maximum load a bearing can carry for
1 million inner-race revolutions with a 90% assurance
the bearing will survive.
Elasticity
The degree to which stress-induced
material deformation reverses in that material after
the stress is removed. A "perfectly elastic"
material completely returns to its original dimensions
after stress is released.
Elastic Limit
The maximum stress which a material
can sustain before permanent deformation takes place.
Elastrohydrodynamic Lubrication
The movement of the lubricant
between two moving surfaces. When two tight-fitting
moving surfaces have a lubricant introduced between
them, the pressure of the lubricant rises. That higher
pressure greatly increases the lubricant's relative
viscosity, moving it into more equal distribution and
film thickness across the surfaces.
EMA
Engine Manufacturers Association
Embrittlement
The process by which a material
loses strength and/or ductility. There are thousands
of types and causes of embrittlement.
Exfoliation
Corrosion which progresses laterally
and parallel to the surface, generally at grain boundaries.
The corrosion products which form work to force metal
away from the body of the material, giving it a layered
appearance.
Extra Light Bearings
Bearings that are narrower and/or
have smaller outside diameters than standard or light
series bearings of the same bore sizes. Generally used
to allow large shafts to fit small housings or small
housings to hold large shafts where the loading is not
severe.
Fatigue
The progressive quality or phenomenon
of materials which leads them to fracture under repeated
or fluctuating stresses when individually, those stresses
are within the material's tensile strength.
Fatigue Strength
The maximum stress that a material
can sustain for a specified (or standardized) number
of stress cycles before it fails.
Filling Notch
Also known as a notch or loading
groove. A filling notch may be cut into the inner race
to allow the final few balls to be loaded during assembly.
Fretting
Uneven wear patterns found on
bearing races due to cycles of sliding or skidding by
the rolling elements that eventually causes corrosion
in the bearing.
Friction
Resistance to motion of one object
over another.
Full-Complement Bearing
A rolling element bearing that
has the maximum possible number of rolling elements
installed by eliminating the cage or retainer. A filling
slot must also be machined into the inner race to facilitate
loading the rolling elements. Full-complement bearings
have higher load ratings but generally sacrifice speed
capacity due to the elimination of the cage or retainer.
Gas Bearing
A particular journal bearing variation.
In place of oil or other liquid-type lubricant, pressurized
gasses are used. Gas bearings can operate higher speeds
and temperature variations than traditionally lubricated
bearings. Gas bearings generally have lower load-bearing
capacities.
Gonio Way
A type of linear motion bearing
which is curved to describe the arc of a pendulum.
Heavywall
Bearing
A specific class of journal bearing
having a wall thickness of at least 0.25" (6.5mm)
and diameter of at least 6" (152mm).
High Carbon Steel
Steel with a high carbon content,
such as a SAE 52100 bearing race. SAE 52100 defines
a steel with a chemical makeup involving 1.0% carbon
and 2% chromium.
Hydrostatic Bearing
A specific type of journal bearing
where the lubricant pressure is from an outside source.
Hydrostatic bearings support loads, even when they are
stopped, because the pumped-in lubricant creates a film
independent of hydrodynamic action.
Insert
The generic term for a bearing
used in a mounted assembly such as a pillow block or
flange unit.
Internal Clearance
The distance between the rolling
elements and the bearing races, also referred to as
fit or radial clearance.
Journal
A round section of shaft that
refers to a specific section of shaft which has been
finished in order to ride in a bearing.
Journal Bearing
A special class of bushing designed
to support a rotating journal, also known as a shell
bearing, plain bearing, or hydrodynamic bearing. A film
of lubricant is supplied in the space between the journal
and the bearing.
Light Bearing
Bearings that are narrower and/or
have smaller outside diameters than standard or light
series bearings of the same bore sizes. Generally used
to allow large shafts to fit small housings or small
housings to hold large shafts where the loading is not
severe.
Load Rating
See Dynamic Operating Capacity.
Lubricant
The material that allows the moving
surfaces of a bearing to move freely, protects against
corrosion, conducts and transfers heat evenly and helps
inhibit contaminants from entering the bearing.
Magnetic
Bearing
A non-contact bearing which operates
by maintaining a magnetic field between two surfaces.
Mohs Hardness Scale
Hardness measured on the Mohs
scale is identified by the numeric hardness assigned
to basic minerals from 1 (softest) to 10 (hardest).
1. Talc
2. Gypsum
3. Clacite
4. Fluorite
5. Apatite
6. Orthoclase
7. Quartz
8. Topaz
9. Corundum
10. Diamond
Needle
Roller Bearing
A type of rolling element bearing
utilizing rollers which are long and thin, carried in
a thin wall cup, often made of drawn mild steel. Usually
there is no inner race; instead, the shaft is hardened
and finished to allow the rolls to ride directly on
it. Needle roller bearings often do not have cages or
retainers.
Normalization
The process of heating a ferrous
alloy material to above the transformation temperature,
then slowly air-cooling, usually to room temperature.
Normalizing re-stabilizes a material, especially after
it has been machined or stressed in any way.
Open Bearing
A ball bearing that does not have
a shield, seal or guard on either of the two sides of
the bearing casing.
Pfund Hardness
Number
A reference standard for the hardness
of a coating on a material measured when a standardized
round-tip quartz or sapphire stylus is applied under
a specific pressure.
Pickling
The removal of surface oxides
by chemical bath or electrochemical reaction.
Quenching
The process of rapidly cooling
metal parts such as bearing races down from their heat
treat furnace temperature. There are a number of quench
opetions, including water tank, oil tank, polymer solution,
and salt.
Radial
Clearance
In an unmounted bearing, the space
between the rolling elements and the races.
RBMEC
Roller Bearing Manufacturing Engineering
Committee.
Retainer
The device used to space, separate
and retain the balls or rollers of a rolling element
bearing; also known as a Cage.
Rockwell Scales
A method of measuring material
hardness calculated from the depth of the indentation
caused by a standardized steel ball or diamond cone
applied under constant load.
Roller Bearing
A special bearing system with
cylindrical rollers capable of handling belted applications,
too large for standard ball bearings.
Rolling Element Bearing
Any bearing where the relative
motion of two surfaces is separated by balls or rollers
as the friction-reducing component. Rolling element
bearings consist of several parts - most have an inner
race, an outer race, rolling elements in between, and
a retainer or cage to separate and position the rolling
elements. At minimum, a rolling element bearing can
be an outer race the rolling elements - held in place
by snap rings or formed portions of the outer race.
Retainers or cages are also optional, and must be deleted
to build a full-complement bearing.
Rubbing Bearing
A type of bearing where the two
surfaces come in contact or rub together, such as an
unlubricated bushing.
SAE
Society of Automotive Engineers,
a trade and standards organization.
SAE Steel Identification
System
The standard method for identifying
the chemical makeup of various steels. Also known as
the AISI system. The content percentages are approximations;
steel is rarely free from contamination by other elements.
These contaminants are generally called inclusions and
noted in the documentation which is supplied with the
shipment.
The system identifies steels by a 4-digit
or 5-digit code:
First digit : the major alloying element
1___ - carbon
2___ - nickel
3___ - nickel-chromium
4___ - molybdenum
5___ - chromium
6___ - chromium-vanadium
7___ - tungsten
8___ - nickel-chromium-molybdenum
9___ - silicon-manganese
Second digit : approximate percentage
of the major allowing element
examples:
_1___ - 1%
_3___ - 3%
52___ - chromium steel with 2% chromium
Third and Fourth digits : approximate
carbon content, as a fractional percent examples:
__30 - 0.30% carbon
__50 - 0.50% carbon
5150 - chromium steel with 1% chromium and 0.50% carbon
52100 - chromium steel with 2% chromium and 1.00% carbon
Sleeve Bearings
A type of bearing with no rolling
elements, where the motor shaft rides on a film of oil.
S-N Diagram
An engineering fatigue failure
analysis tool. S-N diagrams plot the relationship of
stress, S, and the number of cycles, N, before fracture
failure occurs during fatigue testing.
Spalling
Chipping, fragmentation, or separation
of a surface or surface coating and a common cause of
bearing race failure when they are subjected to contamination,
impact or overloading / overheating.
Tensile
Strength
The ratio of a material's strength
to its cross-section.
Thrust Bearing
Bearing designed to operate with
loading only on its axis.
Vickers
Hardness
A reference standard also known
as the Diamond Pyramid Hardness Number (DPHN). A measurement
of the indentation created in a material when a standardized
136-degree-angle pyramid-shaped diamond stylus is applied
under a specific pressure.
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