A tribometer test, ASTM D4172 for oils and D2266 for greases, in which a top steel ball rotates at 1200 rpm against three stationary balls sitting in the lubricant, under 40 kgf at 75 C for 60 minutes. The average scar diameter on the lower balls, typically 0.3 to 0.6 mm, rates antiwear performance. It is a screening tool, good for comparing formulations and weak at predicting life in a real bearing or gear.
Four-ball wear test came in at 0.45 mm on the new AW oil, the old supplier was at 0.38.
Also heard as
- four-ball
- 4-ball wear
- wear scar test
Do not mix it up with
- Four-ball EP test: The wear test runs one moderate load for an hour; the EP test ramps load in short runs until the balls weld.
Related terms
Four-ball EP test
Four-ball test that raises load in ten-second steps until the balls weld, rating extreme pressure capacity.
AW
Antiwear: additives or oils that build protective films to cut wear under moderate boundary contact.
Adhesive wear
Wear where touching asperities weld together and tear, moving metal from one surface to the other.
ZDDP
Zinc dialkyldithiophosphate, the classic antiwear and antioxidant additive in engine and hydraulic oils.