ASTM D2596 for measurement of extreme-pressure properties of lubricating grease
ASTM D2596 for standard test method for measurement of extreme-pressure properties of lubricating grease (Four-Ball method)
6. Apparatus
6.1 Four-Ball Extreme-Pressure Lubricant Tester, illustrated in Fig. 2.

NOTE 1 - It is important to distinguish between the Four-Ball EP Tester and the Four-Ball Wear Tester. The Four-Ball Wear Tester can be used under a variety of test conditions at loads up to 490 N (50 kgf). The Four-Ball EP Tester is designed for testing under more severe conditions and lacks the sensitivity necessary for the Four-Ball Wear Test.

6.2 Microscope, equipped with calibrated measuring scale and readable to an accuracy of 0.01 mm.

6.3 Timer, graduated in tenths of a second.

NOTE 2 - Optional equipment with Four-Ball apparatus consists of a friction-measuring device electrically driven and conveniently graduated in 10-s markings.

7. Materials
7.1 Stoddard Solvent Specifications D235. (Warning - Combustible. Health hazard.)

7.2 ASTM n-Heptane6 (Warning - Flammable. Health hazard.)

7.3 Test Balls - Test balls shall be chrome alloy steel, made from AISI standard steel No. E-52100, with diameter of 12.7 mm (0.5 in.), Grade 25 EP (Extra Polish). Such balls are described in ANSI Specifications B 3, for Metal Balls. The Extra-Polish finish is not described in that specification. The Rockwell C hardness shall be 64 to 66, a closer limit than is found in the ANSI requirement.

8. Preparation of Apparatus
8.1 Thoroughly clean four new test balls, ball pot, and chuck assemblies by first washing with Stoddard solvent (Warning - See 7.1) and then ASTM n-heptane (Warning - See 7.2), and allow to air dry.

8.2 Do not use solvents such as carbon tetrachloride or other solvents that may inherently possess extreme pressure properties which may affect the results.

8.3 Lower the crosshead by raising the lever arm. Lock the lever arm in the raised position by means of a locking arrangement for that purpose.