ASTM D2266 for wear preventive characteristics of lubricating grease
ASTM D2266 standard test method for wear preventive characteristics of lubricating grease (Four-Ball method)
10. Procedure
10.1 Thoroughly clean four test balls, clamping parts for the upper and lower balls and the oil cup using a cleaning fluid or fluids selected in 7.2. Ultrasonic vibration can be used to assist the cleaning process. Wipe the parts using a fresh (unused) lint-free industrial wipe. After cleaning, handle all parts using a fresh wipe. No trace of cleaning fluid should remain when the test oil is introduced and the machine assembled.
10.2 Insert one of the clean test balls into the ball chuck. Insert the ball chuck into spindle of the test machine and tighten according to the equipment manufacture's directions.
NOTE 6 - Insertion of the ball into the ball chuck should require moderate force and result in an audible snap as the test ball enters the ball chuck. The ball should be free from any movement. If the ball rotates or moves within the ball chuck, replace the ball chuck.
10.3 Place a small amount of the grease in the ball cup sufficient to fill the void space between the three balls to be inserted and the bottom of the ball cup. Insert the three test balls in the ball cup and lock the balls in position by hand tightening the locknut into the ball cup using the wrench supplied by the equipment manufacturer.
NOTE 7 - Hand tightening has been found to be between 33.8 and 67.8 N• m (25 to 50 lb• ft.).
10.4 Coat the test balls located in the ball chuck and ball cup completely and thoroughly with the test grease and then fill the ball cup with grease and level off with the top surface of the locknut.
10.5 Place the ball cup assembly containing the three test balls and grease specimen on the test machine. Avoid shock loading by slowly applying the test load.
10.6 After reaching the desired test load, turn on the temperature controller and set the controller to maintain 75 more or less 2°C (167 more or less 4°F).
NOTE 8 - Heater voltage or offset on proportional controllers should be capable of bringing stabilized temperature within the prescribed limits.
10.7 When the desired test temperature is reached, simultaneously start the timer and the drive motor, previously set to 1200 more or less 60 rpm.
10.8 After the drive motor has been on for 60 more or less 1 min., turn off the heaters and drive motor and remove the ball cup and three-ball assembly. (Warning - Parts may be hot at the end of the test. Exercise care when handling parts.)
10.9 Measure the wear scars on the three lower balls to an accuracy of more or less 0.01 mm by one of the following methods:
10.9.1 Option A - Clean the grease from the ball cup assembly without loosening the test balls and wipe the scar area with a tissue. Leave the three balls clamped and set the ball cup assembly on the special base of the microscope that has been designed for this purpose. Make two measurements on each of the wear scars. Take one measurement of the scar along a radial line from the center of the holder; take the second measurement along a line that is 90° from the first measurement. Report the arithmetic average of the six measurements as the scar diameter in millimeters.
10.9.2 Option B - Remove the three lower balls from their clamped position. Wipe the scar area. Take two measurements at 90° to each other. If a scar is elliptical, take one measurement with the striations and the other across the striations. Take care to ensure that the line of sight is perpendicular to the surface being measured. As in Option A, average the six scar readings and report as scar diameter in millimeters.
NOTE 9 - In Test Method D4172, it is stated that if the average of the two measurements on one ball varies from the average of all six readings by more than 0.04 mm, the user should investigate the alignment of the three lower balls with the top ball.
