ASTM D3337 method for determining life and torque of lubricating greases
ASTM D3337 standard test method for determining life and torque of lubricating greases in small ball bearings
8. Procedure
8.1 This procedure describes removal of a used test bearing, installation of a new test bearing, start-up technique, and test monitoring.

8.1.1 Test Bearing Removal:
8.1.1.1 Remove the heater box.

8.1.1.2 Unlatch the radial and axial bead chains from the cantilever beams and unplug the test-bearing outer-race thermocouple cable from the post at the side of the tester.

8.1.1.3 Remove the nose cone by removing the four screws which attach it to the test-bearing housing.

8.1.1.4 Using two small wrenches, one on the test-bearing lock nut and one on the spindle flats next to the nut, loosen the test-bearing lock nut. This is done safely by having the wrench handles about 20 deg apart and squeezing them toward each other to avoid a bending moment on the overhung end of the spindle.

8.1.1.5 Remove the test-bearing lock nut.

8.1.1.6 Slide the test bearing housing off the end of the spindle and lift slowly in a vertical direction until the torque arm, its bead chain, and the thermocouple wires with plug clear the slot in the mounting plate. Do not remove the slinger.

8.1.1.7 Push (Note 1) the used test bearing out of its housing.

NOTE 1 - A 3/8-in. (9.5-mm) diameter by 6-in. (150-mm) long wooden dowel with one end turned down to 1/4 in. (6.4 mm) diameter for 3/16 in. (4.8 mm) is useful in pushing out the test bearing.

8.1.1.8 Rotate the outer race of the used test bearing by hand to determine roughness, stickiness, etc. Tag the bearing, noting date, run number, grease code, running hours, and condition of bearing.

8.1.2 Test Bearing Installation:
8.1.2.1 With the spring-loaded thermocouple retracted, push a new test bearing into the housing. Use the nose cone to seat the test bearing fully. This avoids thumb pressure on the inner race and shields which can damage the bearing.

8.1.2.2 Hold the housing up above the tester and let the thermocouple plug with wires and the radial bead chain drop down through the slot in the mounting plate. Caution: Use care to ensure that the transducer-core extension is not bumped and that the thermocouple lead wires are not bent to prevent erroneous data.

8.1.2.3 Slide the test bearing and housing over the end of the spindle until the test bearing seats against the slinger.

8.1.2.4 Insert the thermocouple plug and attach the radial bead chain to its cantilever with three beads below the beam.

8.1.2.5 Install the test-bearing lock nut (Note 2) finger tight with the shoulder end toward the test bearing. Then fully tighten the nut using two small wrenches and following the technique in 8.1.1.4.

NOTE 2 - If the test bearing runs at temperatures above 300°F (150°C), lubricate the nut and screw threads with a solid lubricant such as molybdenum disulfide to prevent thread galling.

8.1.2.6 Attach the nose cone with the bead chain slot upward using the four small screws.

8.1.2.7 Attach the axial bead chain to its cantilever beam with three beads beyond the beam.

8.1.2.8 Using a 0 to 5-lbf (0 to 22-N) spring scale, check the cantilever beams (Note 3) for 1/2-lbf (2.2-N) radial loading and 5-lbf axial loading.

NOTE 3 - Cantilever beam loads can be changed by bending the beams. After bending, use a 6-in. (150 mm) machinist square and a straightedge to ensure that the radial-bead chain is perpendicular to the base and that the axial bead chain is in line with the centerline of the spindle.

8.1.2.9 Check the thermocouple lead wires to be sure they are freely suspended and smoothly contoured from the torque arm to the plug.

8.1.2.10 Carefully place the heater box over the test-bearing housing.

8.1.3 Start-up Technique:
8.1.3.1 To relieve drive-belt tension, prop up the pivoted-drive motor using a block of wood.

8.1.3.2 Turn the run-time meter to zero.

8.1.3.3 Set the cycle timer to 20 % (zero to 17 % is the 4-h shutdown interval).

8.1.3.4 Set the torque-meter cut-off at 80 % of full scale.

8.1.3.5 Set the temperature controller (left-hand pointer) to about 20°F (10°C) below the intended outer-race test-bearing temperature. Set and maintain the over-temperature cut-off (right-hand pointer) 15°F (9°C) above the control temperature (the temperature controller is connected to the thermocouple in the heater box).

8.1.3.6 Turn on the following switches: 110 V a-c, torque, heater, and high-speed motor. Then push the start button to activate circuits.

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 for about 1/2 min at low speed before removing the prop to bring the spindle up to test speed.

8.1.4 Test Monitoring:
8.1.4.1 After 1 h of test operation at high speed and control temperature, measure the temperature of the outer race of the test bearing. Adjust the controller such that the outer race of the test bearing is at test temperature for the grease. Additional controller adjustment may be required during the first 40 h of operation.

8.1.4.2 After 2 h of test operation at high speed and control temperature, stop the drive motor and prop it up to remove belt tension. Adjust the torque table so that the torque meter reads two to four units up-scale (torque-meter tare) by gently tapping the bead chains with a pencil during the torque table adjustment to minimize the torque-meter tare error due to static friction in the bearings. This ensures torque-transducer contact with the torque arm. Restart the testers and run for another hour before recording data.

8.1.4.3 Record test hours, torque-meter tare, torque-meter reading, net torque, torque in g•cm from calibration curve, control temperature, and outer-race temperature of the test bearing at least once every 24 h. Calibration of torque instrumentation is in A1.5. Torque data for both high-speed and one-r/min operation are to be recorded. After the first recording, set the torque meter cut-off at five times this running torque.

8.1.4.4 To keep the tester running for 30 s when over-torque occurs at start-up, hold the arm away from the transducer core by light finger pressure on the radial bead chain.

8.1.4.5 During the early part of the test at high speed, excessive bead-chain vibration, torque fluctuation greater than more or less 2 g•cm, or torque greater than twice the normal running torque for the grease may be observed. If any of these occur, stop the test and restart using a new test bearing.

9. Results
9.1 Termination of the test is determined by any one of the following conditions:
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 for more than 30 s at high-speed start-up in the test cycle.

9.1.2 Over-temperature of 20°F (11°C) at the outer race of the test bearing.

9.1.3 Noise level increase that persists for more than 1 min either at start-up or running at high speed.