ASTM D3337-91(1996)
(Test Method)Standard Test Method for Determining Life and Torque of Lubricating Greases in Small Ball Bearings
Standard Test Method for Determining Life and Torque of Lubricating Greases in Small Ball Bearings
SCOPE
1.1 This test method describes a procedure for the determination of grease life and torque in small bearings. Although this test method is not the equivalent of a long-time field-service test, it is intended to predict the relative grease life at high temperature in a reasonable period of testing time. In addition, this test method measures the running torque at both low (1 r/min) and high (12000 r/min) speeds.
1.2 Except for torque, which is measured in g[dot]cm, the values stated in inch-pound units are to be regarded as the standard in this test method. The SI values given in parenthesis are for information only.
1.3 This standard does not purport to address all of the safety problems, 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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Standards Content (Sample)
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An American National Standard
Designation: D 3337 – 91 (Reapproved 1996)
Standard Test Method for
Determining Life and Torque of Lubricating Greases in
Small Ball Bearings
This standard is issued under the fixed designation D 3337; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 4. Significance and Use
1.1 This test method describes a procedure for the determi- 4.1 This test method is a screening test to differentiate
nation of grease life and torque in small bearings. Although this among the expected life of greases in ball bearings running at
test method is not the equivalent of a long-time field-service high temperatures. If torque is a factor in selection of a grease,
test, it is intended to predict the relative grease life at high the test method provides for measurements at both low (1
temperature in a reasonable period of testing time. In addition, r/min) and high (12 000 r/min) speeds.
this test method measures the running torque at both low (1
5. Apparatus
r/min) and high (12 000 r/min) speeds.
1.2 Except for torque, which is measured in g·cm, the values 5.1 The apparatus required for this test method is described
in detail in Annex A1. A new R-4 bearing is used for each test.
stated in inch-pound units are to be regarded as the standard in
this test method. The SI values given in parenthesis are for It is run at 12 000 r/min ⁄2-lbf (2.2-N) radial load and 5-lbf
(22-N) axial load.
information only.
1.3 This standard does not purport to address all of the
6. Reagents and Materials
safety concerns, if any, associated with its use. It is the
6.1 Grease Sample—Procure the grease sample from below
responsibility of the user of this standard to establish appro-
the surface of the grease container. Do not let separated oil get
priate safety and health practices and determine the applica-
in contact with the sample; pour the excess oil off if present.
bility of regulatory limitations prior to use.
Screen the grease using a 40-μm retention filter. A technique
2. Terminology
for screening is described in Annex A2.
2.1 Definitions of Terms Specific to This Standard: 6.2 Test Bearing:
6.2.1 Specifications—the test bearing is size R-4.
2.1.1 grease life—a measure of the durability of the grease
in a small bearing at elevated temperatures. 6.2.2 Size—0.2500 in. (6.350 mm) bore, 0.6250 in. (15.875
mm) OD, 0.1960 in. (4.978 mm) wide.
2.1.2 grease torque—a measure of the amount of friction
due to viscous shear of the grease. 6.2.3 Material—Type 440C stainless steel, heat stabilized.
6.2.4 Precision Class—AFBMA (Anti-Friction Bearing
2.1.3 running torque—a measure of the amount of friction
Manufacturers Association) Class 7.
in a rotating bearing due to load, speed, and viscous shear of
the grease. 6.2.5 Radial Clearance—0.0003 to 0.0005 in. (0.007 to
0.013 mm).
3. Summary of Test Method
6.2.6 Retainer—stainless steel ribbon type.
3.1 A single row ball bearing with the test lubricating grease 6.2.7 Shields—removable with snap rings.
is rotated at a high speed under a constant load and selected 6.2.8 Packaging—bearing, shields, and snap rings packaged
temperature. Total running time is determined at completion of individually in clean and sealed envelopes.
the test as a measure of the durability of the grease.
7. Grease Packing of Test Bearing
3.2 Running torque can be obtained for a single row ball
7.1 Pack the test bearing in a clean environment with a
bearing with the test lubricating grease rotating at 1 r/min and
12 000 r/min. quantity of test grease to fill one third of the free space in the
bearing.
This test method is under the jurisdiction of ASTM Committee D-2 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.G on Lubricating Grease. A suitable bearing is Barden No. SR4SSW4, shipped without lubricant and with
Current edition approved Oct. 15, 1991. Published December 1991. Originally shields and snap rings unassembled, available from O. P. Schuman and Sons, Inc.,
e1
published as D 3337 – 74. Last previous edition D 3337 – 74(1985) . County Line and Titus Rd., Warrington, PA 18976.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3337 – 91 (1996)
7.2 If it is necessary to determine the free space of a 8.1.2.1 With the spring-loaded thermocouple retracted, push
weighed bearing, place the bearing (with shields and snap rings a new test bearing into the housing. Use the nose cone to seat
removed) in a container of melted petrolatum of known density the test bearing fully. This avoids thumb pressure on the inner
under vacuum. Let the petrolatum harden, remove bearing, and race and shields which can damage the bearing.
replace shields and snap rings. Clean the bearing of excess 8.1.2.2 Hold the housing up above the tester and let the
petrolatum and determine the weight increase. Using the thermocouple plug with wires and the radial bead chain drop
density of petrolatum and bearing weight increase, compute the down through the slot in the mounting plate. Caution: Use
bearing free space. For the Barden bearing No. SR4SSW4, the care to ensure that the transducer-core extension is not bumped
one-third free space is 0.080 mL. and that the thermocouple lead wires are not bent to prevent
7.3 The test bearing may be packed on either a weight or a erroneous data.
volume basis. A small spatula or a small syringe with a short 8.1.2.3 Slide the test bearing and housing over the end of the
needle can be used to place the test grease between the balls on spindle until the test bearing seats against the slinger.
both sides of the test bearing. 8.1.2.4 Insert the thermocouple plug and attach the radial
7.4 If the test bearing is packed on a weight basis, the bead chain to its cantilever with three beads below the beam.
density of the grease must be known in order to compute the 8.1.2.5 Install the test-bearing lock nut (Note 2) finger tight
weight of test grease equivalent to one-third the free space in with the shoulder end toward the test bearing. Then fully
the test bearing. tighten the nut using two small wrenches and following the
7.5 Immediately after packing the test grease in the test technique in 8.1.1.4.
bearing, install the shields and snap rings. Then turn the
NOTE 2—If the test bearing runs at temperatures above 300°F (150°C),
bearing 100 revolutions in each direction at less than 200 r/min
lubricate the nut and screw threads with a solid lubricant such as
to distribute the test grease.
molybdenum disulfide to prevent thread galling.
8.1.2.6 Attach the nose cone with the bead chain slot
8. Procedure
upward using the four small screws.
8.1 This procedure describes removal of a used test bearing,
8.1.2.7 Attach the axial bead chain to its cantilever beam
installation of a new test bearing, start-up technique, and test
with three beads beyond the beam.
monitoring.
8.1.2.8 Usinga0to 5-lbf (0 to 22-N) spring scale, check the
8.1.1 Test Bearing Removal:
cantilever beams (Note 3) for ⁄2-lbf (2.2-N) radial loading and
8.1.1.1 Remove the heater box.
5-lbf axial loading.
8.1.1.2 Unlatch the radial and axial bead chains from the
NOTE 3—Cantilever beam loads can be changed by bending the beams.
cantilever beams and unplug the test-bearing outer-race ther-
After bending, use a 6-in. (150 mm) machinist square and a straightedge
mocouple cable from the post at the side of the tester.
to ensure that the radial-bead chain is perpendicular to the base and that
8.1.1.3 Remove the nose cone by removing the four screws
the axial bead chain is in line with the centerline of the spindle.
which attach it to the test-bearing housing.
8.1.2.9 Check the thermocouple lead wires to be sure they
8.1.1.4 Using two small wrenches, one on the test-bearing
are freely suspended and smoothly contoured from the torque
lock nut and one on the spindle flats next to the nut, loosen the
arm to the plug.
test-bearing lock nut. This is done safely by having the wrench
8.1.2.10 Carefully place the heater box over the test-bearing
handles about 20 deg apart and squeezing them toward each
housing.
other to avoid a bending moment on the overhung end of the
8.1.3 Start-up Technique:
spindle.
8.1.3.1 To relieve drive-belt tension, prop up the pivoted-
8.1.1.5 Remove the test-bearing lock nut.
drive motor using a block of wood.
8.1.1.6 Slide the test bearing housing off the end of the
8.1.3.2 Turn the run-time meter to zero.
spindle and lift slowly in a vertical direction until the torque
8.1.3.3 Set the cycle timer to 20 % (zero to 17 % is the 4-h
arm, its bead chain, and the thermocouple wires with plug clear
shutdown interval).
the slot in the mounting plate. Do not remove the slinger.
8.1.3.4 Set the torque-meter cut-off at 80 % of full scale.
8.1.1.7 Push (Note 1) the used test bearing out of its
8.1.3.5 Set the temperature controller (left-hand pointer) to
housing.
about 20°F (10°C) below the intended outer-race test-bearing
NOTE 1—A ⁄8-in. (9.5-mm) diameter by 6-in. (150-mm) long wooden
temperature. Set and maintain the over-temperature cut-off
1 3
dowel with one end turned down to ⁄4 in. (6.4 mm) diameter for ⁄16 in.
(right-hand pointer) 15°F (9°C) above the control temperature
(4.8 mm) is useful in pushing out the test bearing.
(the temperature controller is connected to the thermocouple in
8.1.1.8 Rotate the outer race of the used test bearing by hand
the heater box).
to determine roughness, stickiness, etc. Tag the bearing, noting
8.1.3.6 Turn on the following switches: 110 V a-c, torque,
date, run number, grease code, running hours, and condition of
heater, and high-speed motor. Then push the start button to
bearing.
activate circuits.
8.1.2 Test Bearing Installation:
8.1.3.7 Gradually slide the prop out from under the drive-
motor base until the spindle runs at low speed with a slack belt.
Finger pressure on the spindle aids in keeping a low speed. Run
A suitable micrometer syringe is Catalog No. N-07844-00, 0.2-mL capacity,
for about ⁄2 min at low speed before removing the prop to
manufactured by Cole-Parmer Instruments Co., 7425 North Oak Park Ave.,
Chicago, IL 60648. bring the spindle up to test speed.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3337 – 91 (1996)
FIG. 1 Weibull Parameter of Grease A
8.1.4 Test Monitoring: bearing at least once every 24 h. Calibration of torque
8.1.4.1 After1hof test operation at high speed and control instrumentation is in A1.5. Torque data for both high-speed and
temperature, measure the temperature of the outer race of the one-r/min operation are to be recorded. After the first record-
test bearing. Adjust the controller such that the outer race of the ing, set the torque meter cut-off at five times this running
test bearing is at test temperature for the grease. Additional torque.
controller adjustment may be required during the first 40 h of
8.1.4.4 To keep the tester running for 30 s when over-torque
operation.
occurs at start-up, hold the arm away from the transducer core
8.1.4.2 After2hof test operation at high speed and control
by light finger pressure on the radial bead chain.
temperature, stop the drive motor and prop it up to remove belt
8.1.4.5 During the early part of the test at high speed,
tension. Adjust the torque table so that the torque meter reads
excessive bead-chain vibration, torque fluctuation greater than
two to four units up-scale (torque-meter tare) by gently tapping
6 2 g·cm, or torque greater than twice the normal running
the bead chains with a pencil during the torque table adjust-
torque for the grease may be observed. If any of these occur,
ment to minimize the torque-meter tare error due to static
stop the test and restart using a new test bearing.
friction in the bearings. This ensures torque-transducer contact
with the torque arm. Restart the testers and run for another hour
9. Results
before recording data.
8.1.4.3 Record test hours, torque-meter tare, torque-meter 9.1 Termination of the test is determined by any one of the
following conditions:
reading, net torque, torque in g·cm from calibration curve,
control temperature, and outer-race temperature of the test
9.1.1 Instantaneous over-torque of five times the minimum
running torque at high speed and test temperature, or over-
torque of five times the minimum running torque if it continues
A miniature recorder with a chart speed of ⁄4-in./h is useful for monitoring
for more than 30 s at high-speed start-up in the test cycle.
outer-race temperature throughout the entire test. To set the controller, the outer-race
9.1.2 Over-temperature of 20°F (11°C) at the outer race of
temperature of the test bearing should be measured to 62°F (6 1°C) using a
precision instrument such as a potentiometer. the test bearing.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3337 – 91 (1996)
FIG. 2 Weibull Parameter of Grease B
TABLE 1 Suggested Report Form for Evaluation of Greases in Small Bearings
Grease: Date:
Temperature, °F (°C) Operator
Speed, r/min
Load, lb: Radial Avg running-life from
Axial three runs, h
Torque g-cm
Box
Minimum 1 Minimum Failure Outer Race, Control,° F Running Reason for
Run No. r/min High r/min High r/min °F(°C) Rise (°C) Life, h Failure
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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D 3337 – 91 (1996)
TABLE 3 Precision—Summary of Cooperative Testing Program
9.1.3 Noise level increase that persists for more than 1 min
either at start-up or running at high speed. Failure Lives, h
Mean Range for Center
50 % of Results
10. Report
Grease A 151 130 to 180
10.1 Report test results and test conditions on the report
Grease B 297 220 to 388
form shown in Table 1.
11. Precision and Bias
therefore, are not appropriate. Weibull parameters such as
sl
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