8. Standardization of Thrust Loading Device
8.1 Pack a bearing, install it into the holder and place the assembly into a plastic jar as described in 10.1 through 10.4. Place the jar onto the base of the motor drive spindle and center it under the indexing pin of the drive. Lower the drive until the O ring just contacts the 1-kg weight. Run the bottom nut of the depth gage (see Fig. 3) down to the stop. Place a 3-mm spacer on top of this nut. Bring the top nut down to the spacer. While holding the top nut in position, remove the spacer and run the bottom nut up and tighten it against the top nut. When the O ring is compressed against the 1-kg weight until the adjustment nut hits the stop, there will be a 29-N load added, giving a total load of 39 N on the bearing. (The loads described are provided by the forces of the spring in the thrust loading spindle and sum of the 1-kg weight and spring, respectively. These loads are approximate. The 1-kg weights should be within 0.010 kg of their stated values. The thrust loading spindle should be calibrated by some suitable method when it is first put into service, recalibrated periodically, and replaced if its spring does not provide sufficient force to spin the test bearings without slippage during the 60 s run to distribute the grease.) Examine the O ring periodically and replace it if it shows any cracks or other signs of deterioration.
8.2 The thrust loading device should be standardized before use, once per day if used daily, and again if there is reason to believe that the standardization has changed. The thrust loading device may be standardized using one of the greases to be tested.
