ASTM D4172 for wear preventive characteristics of lubricating fluid (Four-ball method)
4. Summary of Test Method
4.1 Three 12.7-mm [1/2-in.] diameter steel balls are clamped together and covered with the lubricant to be evaluated. A fourth 12.7-mm diameter steel ball, referred to as the top ball, is pressed with a force of 147 or 392 N [15 or 40 kgf] into the cavity formed by the three clamped balls for three-point contact. The temperature of the test lubricant is regulated at 75°C [167°F] and then the top ball is rotated at 1200 rpm for 60 min. Lubricants are compared by using the average size of the scar diameters worn on the three lower clamped balls.
NOTE 1 - Because of differences in the construction of the various machines on which the four-ball test can be made, the manufacturer's instructions should be consulted for proper machine set up and operation.
NOTE 2 - Although the test can be run under other parameters, the precision noted in Section 10 may vary. No aqueous fluid was included in the round-robin to establish the precision limits.
5. Significance and Use
5.1 This test method can be used to determine the relative wear preventive properties of lubricating fluids in sliding contact under the prescribed test conditions. No attempt has been made to correlate this test with balls in rolling contact. The user of this test method should determine to his own satisfaction whether results of this test procedure correlate with field performance or other bench test machines.
