9. Procedure
9.1 Place the three test balls in the test-lubricant cup. Place the lock ring over the test balls and screw down the nut securely (Note 5). Pour the lubricating fluid to be tested over the three test balls until they are covered.
NOTE 5 - Subsequent independent investigations reported in 1971 by several laboratories indicate that optimum test repeatability is obtained when the force on the lock-down nut is maintained within the range 68 more or less 7h•m (50 more or less 5ft•lb), applied, and measured by means of a torque wrench. Significantly lower weld points were obtained when the force applied was approximately 136N•m (100ft•lb).
9.2 Bring the lubricant and cup to 18 to 35°C (65 to 95°F).
9.3 Press one ball into the ball chuck (Note 6) and mount the chuck into the chuck-holder.
NOTE 6 - Examine the chuck and top ball after each run. If the ball shows signs of movement in the chuck, even though welding of the four-balls did not occur, the chuck should be replaced. When welding occurs slippage between ball and chuck nearly always occurs. If the chuck has metal from the top ball adhering to it, the metal must be removed or the chuck replaced.
9.4 Install the test-lubricant cup assembly on the test apparatus in contact with the fourth ball. Place the spacer between cup and thrust bearing.
9.5 Place the weight tray and sufficient weights on the horizontal arm in the correct notch for a base test load of 784N (80kg). Release the lever arm and gently apply (Note7) the test load to the balls, making certain the cup assembly and spacer are centered. If the optional friction-measuring device is used, connect the calibrated arm on the test-lubricant cup to the indicator spring by means of the clip and wire.
NOTE 7 - Shock-loading should be avoided as it may deform the balls permanently.
9.6 Start the motor and run for 10 more or less 2s.
NOTE 8 - The time for the apparatus to "coast" to a stop is not considered.
9.7 Remove the test-lubricant cup assembly; remove the chuck and discard the ball.
9.8 Measure the scar diameter of test balls as follows:
9.8.1 Option A - Remove the tes tballs. Clean the balls with cleaning solvent (see 7.1) and then rinse solvent (see 7.2). Wipe dry with a soft cloth. Place the individual balls on a suitable holder and by means of a microscope, measure to the nearest 0.01mm the scar diameters both parallel (horizontal) and normal (vertical) to the striations in the scar surface of one of the three test balls (Note 9).
9.8.2 Option B - Leave the balls clamped in the cup. Pour out the lubricating fluid. Wash the ball surfaces with cleaning solvent (see 7.1) and then the rinse solvent (see 7.2). Using a microscope, measure to the nearest 0.01mm the scar diameters both parallel (horizontal) and normal (vertical) to the striations in the scar surface of one of the three test balls (Note 9).
9.8.3 Measurements by microscope of the scar diameters on all three balls, rather than one ball as outlined in Options A or B, may be made if the operator so desires.
NOTE 9 - It is recommended that prior to selection of Option A or B, the operator examines visually the test balls to ascertain no gross discrepancy in the wear scars formed on the test balls; if discrepancy is noted, then wear scar measurements on all three test balls must be made.
9.9 Record (Table 1, Column 2) for the 784N (80-kg) load the average scar diameter by any one of the three techniques described in 9.8. Compare this average scar diameter with the compensation scar diameter (Table 1, Column 3).
9.10 Make additional runs at consecutively higher test loads (Table 1, Column 1), recording the measured scar diameter(s) (Note 10) and discarding test balls, until welding occurs (Note 11). Make a check run at this point. If welding does not occur on the check run, repeat the test at the next higher load until welding is verified.
NOTE 10 - Measuring the scar diameter(s) of test balls in the incipient and immediate seizure region is sometimes difficult due to the flow of metal obliterating the full contact area formed by the rotating ball. In such cases the metal flow can generally be removed or peeled off with a suitable instrument. See Figs. 4 and 5. If the scar periphery is obscure or not well defined an estimate of the scar diameter is made. See Figs.6 and 7.
NOTE 11 - Shut off the motor immediately to prevent damage to the tester. Excessive seizure between the ball and ball chuck may result if caution is not observed. Welding may be detected by any or all of the following: (1) If friction-measuring device is used, a sharp transverse movement of the indicating pen, (2) increased noise level of motor, (3) smoking from test-oil cup, (4) a sudden drop in the lever arm.
9.11 If the measured scar diameter for the 784 N (80-kg) load is more than 5% from the compensation scar diameter, make the next run at the next lower load (Table 1, Column 1). Continue this procedure until the last nonseizure load is determined.
NOTE 12 - When the optional friction-measuring device is used, the last nonseizure load is detected by a gradual transverse movement of the indicating pen.
9.12 Alternatively, in instances when the measured wear scars remain more than 5 % above the compensation line, continue this procedure until a total of ten runs below the weld point is recorded.
