ASTM G182-06
(Test Method)Standard Test Method for Determination of the Breakaway Friction Characteristics of Rolling Element Bearings
Standard Test Method for Determination of the Breakaway Friction Characteristics of Rolling Element Bearings
SIGNIFICANCE AND USE
This test is a simple, effective way of determining the ability of bearings to roll freely. Most bearing manufacturers do not supply information on the breakaway friction coefficient of their products and if this is a design factor, users often buy candidate bearings and try them until they find one that appears to operate freer than the others. This test allows quantification of the breakaway friction characteristics of bearings. This test assesses the friction of a bearing as a tribosystem which includes its construction and lubrication. It has shown to correlate with use. If a bearing has a low breakaway angle in this test, its breakaway friction will be lower in service than the same size bearings that displayed a higher breakaway angle in this test.
Breakaway friction of bearings is important in instruments where forces are light and the bearings are used as pivots rather than for continued rotation. Low friction is often imperative for proper device operation.
Bearings with low breakaway friction are often sought for web handling rollers. Many rollers are driven only by tangential web contact and slippage can often damage the web. Low friction bearings are required.
This test is useful for screening bearings for any applications where breakaway friction is a design concern.
SCOPE
1.1 This test method is an extension of Test Method G 164 and uses an inclined plane and a paperclip rider to detect the presence or absence of lubricants on the surfaces of flexible webs. A study to identify free spinning or low rolling friction bearings indicated that the paperclip friction test could be used for rolling friction by simply replacing the paperclip with a rolling element bearing on an axle. The angle of the inclined plane at initiation of rolling is the breakaway angle. This test method can be used to measure the angle at breakaway of small diameter (up to 100 mm outside diameter) rolling element bearings. The bearings that have been tested in the development of this method are conventional ball bearings with different separators, seals, and different conditions of lubrication (none, oil, greases, and so forth), but there is no technical reason why this test method would not work with bearings of other design, including plain bearings. Rolling element bearings like any sliding system can have friction characteristics at breakaway that are different than rolling continuously. As is the case with most inclined plane friction tests, the test only produces the friction characteristic at the onset of measurable rolling, using the angle () when measurable rolling commences. The objective of this test is an assessment of breakaway rolling friction characteristics to assist machine designers in the selection of rolling element bearings for instrument pivots and the like where breakaway friction is a concern.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: G182 − 06
StandardTest Method for
Determination of the Breakaway Friction Characteristics of
Rolling Element Bearings
This standard is issued under the fixed designation G182; 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 2. Referenced Documents
1.1 This test method is an extension of Test Method G164 2.1 ASTM Standards:
and uses an inclined plane and a paperclip rider to detect the G40 Terminology Relating to Wear and Erosion
presence or absence of lubricants on the surfaces of flexible G117 Guide for Calculating and Reporting Measures of
webs. A study to identify free spinning or low rolling friction Precision Using Data from Interlaboratory Wear or Ero-
bearings indicated that the paperclip friction test could be used sion Tests
for rolling friction by simply replacing the paperclip with a G143 Test Method for Measurement of Web/Roller Friction
rolling element bearing on an axle. The angle of the inclined Characteristics
plane at initiation of rolling is the breakaway angle. This test G164 Test Method for Determination of Surface Lubrication
methodcanbeusedtomeasuretheangleatbreakawayofsmall on Flexible Webs
diameter (up to 100 mm outside diameter) rolling element
3. Terminology
bearings. The bearings that have been tested in the develop-
3.1 Definitions Relating to Wear and Erosion (taken from
ment of this method are conventional ball bearings with
Terminology G40):
different separators, seals, and different conditions of lubrica-
3.1.1 coeffıcient of friction, µ—in tribology, the dimension-
tion (none, oil, greases, and so forth), but there is no technical
less ratio of the friction force (F) between two bodies to the
reason why this test method would not work with bearings of
normal force (N) pressing these bodies together.
other design, including plain bearings. Rolling element bear-
ings like any sliding system can have friction characteristics at
3.1.2 friction force—the resisting force tangential to the
breakawaythataredifferentthanrollingcontinuously.Asisthe
interface between two bodies when, under the action of
case with most inclined plane friction tests, the test only
external force, one body moves or tends to move relative to the
produces the friction characteristic at the onset of measurable
other.
rolling, using the angle (θ) when measurable rolling com-
3.1.3 kinetic coeffıcient of friction—the coefficient of fric-
mences. The objective of this test is an assessment of break-
tion under conditions of macroscopic relative motion between
awayrollingfrictioncharacteristicstoassistmachinedesigners
two bodies.
in the selection of rolling element bearings for instrument
3.1.4 lubricant—any substance interposed between two sur-
pivots and the like where breakaway friction is a concern.
facesforthepurposeofreducingthefrictionandwearbetween
1.2 The values stated in SI units are to be regarded as
them.
standard. No other units of measurement are included in this
3.2 Definitions Not Covered by Terminology G40:
standard.
3.2.1 breakaway coeffıcient of rolling friction—the force in
1.3 This standard does not purport to address all of the
the direction of rolling (F) required to produce rolling of a
safety concerns, if any, associated with its use. It is the
revoluteshapeonasurface,dividedbythenormalforce (N)on
responsibility of the user of this standard to establish appro-
the revolute shape:
priate safety and health practices and determine the applica-
F
bility of regulatory limitations prior to use.
µ rolling 5 (1)
N
1 2
This test method is under the jurisdiction of ASTM Committee G02 on Wear For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Erosion and is the direct responsibility of Subcommittee G02.50 on Friction. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved May 1, 2006. Published May 2006. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
G0182-06. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G182 − 06
3.2.2 inclined plane—asurfacethatcanberaisedatanangle 6. Apparatus
to produce motion of an object on the plane.
6.1 Bearing Axle—The test bearing is clamped between two
3.2.3 plain bearings—a cylindrical shape used to support a tapered plugs assembled on the threaded-rod rider shown in
rotating shaft. Fig. 1. The tapered plugs are tightened such that the inner race
of the bearing is fixed to and centered on the horizontal portion
3.2.4 rolling—motion of revolute shape (ball, wheel, roller,
of the threaded rod.
andsoforth)inaspecificdirection,onasurfacesuchthatthere
6.2 Weights—The normal force of the bearing on the in-
is no relative slip in all or part of the area of contact.
clined plane is produced by the cumulative mass of the bearing
3.2.5 rolling element bearing—balls or rollers in raceways
andtheriderassemblythatholdsthebearing.Theweightofthe
that support a shaft and allow rotation of the shaft or bearing
rider (without the bearing) shall be 90 to 100 g and the
outer race (OD).
assemblyshouldweighbetween100and130g.Theassembled
test bearing and rider should weigh the same for each test
4. Summary of Test Method
bearing. Weights in the form of bushings or washers can be
4.1 This test method can be used to measure the breakaway
affixed to the axle portion of the rider to make all test
rolling friction characteristics of rolling element bearings. assemblies have the same weight (65 g). Weights must be
added in pairs with equal amounts on each side of the rider.
4.2 Small rolling element bearings (less than 100 mm
6.3 Inclined Plane—The inclined plane should be from 20
outside diameter) are affixed to a balanced rider and placed on
to30mmwide,aminimumof250mmlong,bearigidmaterial
an incline. The rider is designed so that it becomes the axle
(hard plastic, metal, etc.) and be capable of being raised on a
about which the bearing rotates. The inclined plane is raised
pivot and locked in place at the rider breakaway angle. The
(by hand or mechanism) until the outer race (OD) of the
inclined plane should be high enough to allow unobstructed
bearing starts to roll on the inclined plane. The inclined plane
rolling of the rider down the plane (Fig. 2).
surface is covered with a plasticized PVC tape to increase the
static friction between the outside surface of the bearing and
6.4 Rolling Surface—The inclined plane should be covered
inclined plane. The test will not yield rolling friction charac-
by a single layer of 127/152 µm inch-thick plasticized PVC
teristics if the bearing slides rather than rolls on the inclined
tape (black electrical tape) with the pressure sensitive adhesive
plane.
(PSA) surface adhered to the plane. The tape must be wider
thanthetestbearingbyatleast2mmoneachside.Thepurpose
4.3 The rolling friction characteristics measured by this test
of the tape is to increase the friction between the outer race and
are the net result of the bearing design, materials and state of
the inclined plane. Tests with Test Method G143 capstan
lubrication. Thus this test could also be used to evaluate
friction test identified this material as having high frict
...
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