Four Ball Wear Test

Definition

Four Ball Wear Test determines a lubricant's antiwear properties under boundary lubrication (metal to metal contact). Three steel balls are clamped together to form a cradle upon which a fourth ball rotates on a vertical axis. The balls are immersed in the oil sample at a specified speed, temperature and load. At the end of a specified test time, the average diameter of the wear scars on the three lower balls is measured. During the test, the load is increased every 10 minutes up to the point where the frictional trace indicates incipient seizure. The coefficient of friction is measured at the end of each 10 min interval.

Standard Test Method Used

ASTM D5183

Reporting Measurement

mm, kgf (kilogram force)

Amount of Sample Needed

200 mL