ASTM F2488-05(2022)

Standard Terminology for Rolling Element Bearings

SCOPE
1.1 This terminology covers terms and their definitions relevant to the materials and processes associated with rolling element bearings.  
1.2 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Dec-2021
• ICS: 01.040.21 - Mechanical systems and components for general use (Vocabularies)
• ICS: 21.100.01 - Bearings in general
• Technical Committee: F34 - Rolling Element Bearings
• Drafting Committee: F34.91 - Editorial and Terminology

Overview

ASTM F2488-05(2022) - Standard Terminology for Rolling Element Bearings establishes a comprehensive vocabulary relating to the materials and processes associated with rolling element bearings. Published by ASTM International, this standard supports universal understanding by defining key technical terms critical for the design, manufacture, testing, and application of rolling element bearings across industries. This terminology standard is developed in line with globally recognized principles from the World Trade Organization Technical Barriers to Trade (TBT) Committee, ensuring international consistency and harmonization.

Key Topics

ASTM F2488-05(2022) provides clear definitions for essential terms relating to rolling element bearings, improving communication and reducing ambiguities in specification or procurement. Major topics and terms include:

• Bearing Components: Definitions such as ball gage, ball grade, case depth, and stepped inner ring clarify component tolerances and material specifications.
• Lubrication and Fluid Properties: Key terminology like absolute viscosity, boundary lubrication, oxidation stability, and kinematic viscosity support effective lubricant selection and performance evaluation.
• Additives and Chemical Characteristics: Terms such as additives, antioxidants, corrosion inhibitors, and acid number assist in understanding lubricant functionality and longevity.
• Wear and Failure Modes: Definitions surrounding wear, fretting corrosion, compatibility, contamination, and corrosion provide insight into bearing failure mechanisms and maintenance considerations.
• Measurement Units and Acronyms: Standard measurement units (centipoise, centistoke, poise) as well as industry acronyms (ABEC, VIMVAR) are specified for clarity in technical documentation and communication.
• Performance Indicators: Concepts like average life (L50), rating life (L10), DN value, nDm value, repeatability, and reproducibility help in predicting bearing lifespan and specifying operational limits.

Applications

The terminology defined in ASTM F2488-05(2022) is widely applicable across industries utilizing rolling element bearings in mechanical assemblies. Key application areas include:

• Specification and Procurement: Ensures precise, unambiguous communication in contracts, maintenance manuals, and technical publications.
• Quality Assurance and Inspection: Provides standardized references for inspection criteria, testing methods, and performance validation.
• Research and Development: Facilitates innovation and international collaboration by using consistent industrial vocabulary.
• Training and Education: Serves as an authoritative resource for engineers, technicians, and industry professionals learning about rolling element bearing technology.
• Maintenance and Reliability Analysis: Enhances understanding of lubricant compatibility, wear mechanisms, and performance indicators crucial for proactive bearing maintenance.

Related Standards

For comprehensive guidance in the field of rolling element bearings and related terminology, consider these associated standards:

• ASTM F2215 - Standard Specification for Balls, Bearings, Ferrous and Nonferrous for Use in Bearings
• ASTM D2425 - Standard Test Method for Viscosity of Oils
• ASTM D445 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids
• ISO 5593 - Rolling Bearings - Vocabulary
• ABMA Standards - Covering tolerances, fitting practices, and performance of rolling bearings

By adopting ASTM F2488-05(2022) and its related standards, organizations support best practices in bearing terminology, drive quality and compliance, and foster successful global business and engineering operations.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2488 − 05 (Reapproved 2022)
Standard Terminology for
Rolling Element Bearings
This standard is issued under the fixed designation F2488; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope ball gage (S), n— prescribed small amount by which the lot
mean diameter should differ from nominal diameter, this
1.1 This terminology covers terms and their definitions
amount being one of an established series of amounts.
relevant to the materials and processes associated with rolling
DISCUSSION—A ball gage, in combination with the ball grade and
element bearings.
nominal ball diameter, should be considered as the most exact ball size
1.2 This international standard was developed in accor-
specification to be used by a customer for ordering purposes.
dance with internationally recognized principles on standard-
ball gage deviation (∆S), n—difference between the lot mean
ization established in the Decision on Principles for the
diameter and the sum of the nominal diameter and the ball
Development of International Standards, Guides and Recom-
gage.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
ball grade (G), n—specific combination of dimensional form
and surface roughness tolerances.Aball grade is designated
2. Terminology
by a grade number followed by the letter “C” indicating
silicon nitride ceramic.
2.1 Definitions:
absolute viscosity (η), n—(sometimes called dynamic viscos-
boundary lubrication, n—condition of lubrication in which
ityorjust viscosity)—ameasureofthetendencyofthefluid
the friction between two surfaces in relative motion is
to resist shear.
determined by the roughness of the surfaces and by the
properties of the lubricant other than viscosity.
acid number, n—measure of the quality of a lubricant. High
DISCUSSION—Antiwear and extreme pressure additives reduce the
acid numbers (much higher than the fresh oil) are an
wear of components operating under this regime.
indication of lubricant oxidation/degradation.
DISCUSSION—Oils with high acid numbers should not be used. Acid
case depth, n—thickness, measured radially from the surface
number is measured as milligrams of KOH needed to neutralize1gof
of the hardened case to a point at which carbon content or
oil.
hardness becomes the same as the ball core.
additive, n—any chemical compound added to a lubricant to
centipoise, n—unit of dynamic viscosity.
improve or meet special needs necessary for service (formu-
DISCUSSION—The unit in the cgs system is 1 centipoise (cP). The SI
lated lubricants). The most important additives are
unit of dynamic viscosity is 1 Pa-s and equivalent to 10 cP.
antioxidants, rust, and corrosion inhibitors, and extreme
pressure (EP) and antiwear (AW) additives.
centistoke, n—unit of kinematic viscosity.
DISCUSSION—The unit in the cgs system is 1 centistoke (cSt). The SI
antioxidants (oxidation inhibitors), n— chemical compounds
2 6
unit of kinematic viscosity is 1 m /s and is equivalent to 10 cSt.
used to improve the oxidation stability and subsequent
compatibility, n—measure of the ability of a lubricant to be
deterioration of lubricants.
mixed with other lubricants or bearing preservatives (fluids
average life (L ), n—for a radial roller bearing, the number of
that form films on metal surfaces to prevent corrosion during
revolutionsthat50 %ofagroupofbearingswillcompleteor
storage) to form a uniform mixture without causing any
exceed before the first evidence of fatigue develops.
resultant reaction or precipitation of material. Compatibility
DISCUSSION—The average life maybe as much as five times the rating
isalsoameasureoftheabilityofalubricantnottocauseany
life.
detrimental effect to metal, plastic, or elastomer materials.
DISCUSSION—It is recommended that any preservative material be
removed from bearings before lubrication.
This terminology is under the jurisdiction ofASTM Committee F34 on Rolling
Element Bearings and is the direct responsibility of Subcommittee F34.91 on
contamination, n—(1) presence of mostly solid foreign mate-
Editorial and Terminology.
rials like sand, grinding powder, dust, and so forth, in a
Current edition approved Jan. 1, 2022. Published January 2022. Originally
lubricant that might cause an increase in wear, torque, and
approved in 2005. Last previous edition approved in 2013 as F2488 – 05(2013).
DOI: 10.1520/F2488-05R22. noise and result in reduced bearing life; and (2) presence of
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2488 − 05 (2022)
fluids like water, solvents, and other oils that might cause fretting corrosion, n—special type of wear produced on
accelerated oxidation, washout, rusting, or crystallization of materials in intimate contact that are subjected to the
the additives and other phenomena that reduce a bearing’s combined action of oscillatory motions of small amplitudes
life. and high frequencies. Fretting corrosion appears similar to
atmospheric corrosion (rust) as a reddish-brown layer on
corrosion, n—gradual destruction of a metal surface as a result
steel surfaces.
of chemical attack caused by polar or acidic agents like
interfacial tension, n—when two immiscible liquids are in
humidity (water), compounds formed by lubricant
deterioration, or contaminants from the environment. contact, their interface has many characteristics in common
with a gas-liquid surface.This interface possesses interfacial
corrosion inhibitors, n—corrosion inhibitors protect metal
free energy because of the unbalanced attractive forces
surfaces against corrosion or rust by forming a protective
exerted on the molecules at the interface by the molecules
coating or by deactivation of corrosive compounds formed
within the separate phases. This free energy is called the
during the operation of a bearing.
interfacial tension.
density, n—mass per unit volume of a substance.
kinematic viscosity, n—ratio of absolute viscosity to fluid
DISCUSSION—The cgs unit of density (ρ) is 1 g/cm , and the SI unit
density.
of density is 1 kg/m . Density depends on the chemical composition
DISCUSSION—This ratio arises frequently in lubrication analyses, and
and in itself is no criterion of quality. It is a weak function of
thus, kinematic viscosity has become a separate term describing the
temperature and pressure for liquids and solids.
viscosity of a fluid. Many experimental measurements of viscosity of
fluids result in a measure of kinematic viscosity from which absolute
deviation from spherical form (∆Rw), n—greatest radial
viscosity is calculated. See absolute viscosity. The cgs unit of
distance in any radial plane between a sphere circumscribed
kinematic viscosity is cSt and the SI unit is m /s. The viscosity of a
around the ball surface and any point on the ball surface.
PREB oil is a major factor in lubricant selection. The viscosity is
directly involved in frictional, thermal, and fluid film conditions that
DN value, n— product of the bearing bore diameter in
reflect the influence of load, speed, temperature, and design character-
millimetres multiplied by the speed in revolutions per
istics of the bearing being lubricated.
minute (compare to nD value).
m
marking increments, n—standard unit steps to express the
dynamic viscosity, n—another name for absolute viscosity.
specific diameter.
EP lubricants (extreme pressure lubricants), n—lubricants
mineral oil, n—oils based on petroleum stocks. These oils
(oil or greases) that contain extreme pressure additives to
come in two types, naphthenic and paraffinic. The naph-
protect the bearings against wear and welding (scoring).
thenic oils contain unsaturated hydrocarbons, usually in the
form of aromatic species. The paraffinic oils are primarily
esters, n—esters are formed from the reaction of acids and
saturated hydrocarbons with only low levels of unsaturation.
alcohols. Esters form a class of synthetic lubricants.
DISCUSSION—Esters of higher alcohols with divalent fatty acids form
nD value (index), n—also called speed index—relative
m
diester lubricants while esters of polyhydric alcohols are called the
indicator of the lubricant stress imposed by a bearing
polyol ester lubricants.These latter esters have higher viscosity and are
rotating at a given speed, where n is the rotational speed of
more heat resistant than diesters.
the rolling element bearing in revolutions per minute and D
m
is the mean diameter in millimetres (arithmetic mean of bore
evaporation loss, n—lubrication fluid losses occurring at
diameter d and outside diameter D).
higher temperatures or under vacuum, or both, as a result of
DISCUSSION—The speed index is multiplied by a factor k depending
evaporation. a
on the roller element bearing type:
DISCUSSION—This can lead to an increase in lubricant consumption
k = 1 for deep groove ball bearings, angular contact ball bearings,
a
and also to an alteration of the fluid properties of a lubricant (especially
self-aligning ball bearings, radially loaded cylindrical roller bearings,
an increase in the viscosity of blended lubricants).The evaporation loss
-6 and thrust ball bearings;
is expressed as a weight loss in milligrams (10 kg) or wt %.
k = 2 for spherical roller bearings, taper roller bearings, and needle
a
roller bearings; and
fire point, n—lowest temperature at which the vapor or a
k = 3 for axially loaded cylindrical roller bearings and full
a
lubrication fluid ignites under specified test conditions and
complement roller bearings.
continues to burn for at least 5 s without the benefit of an
The factor k takes into account the various rates of sliding friction
a
outside flame. The fire point is a temperature above the flash
that usually occurs during the operation of a rolling element bearing.
point.
The nD value is an aid in choosing a suitable lubricant viscosity for
m
DISCUSSION—Perfluoropolyethers have no fire point. agivenbearingspeedandisparticularlyapplicabletogrease-lubricated
bearings.
flash point, n—lowest temperature of a lubrication fl
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