SAE ARP 6255A:2025-05-16

Employing “ball-on-ring” philosophy, a nonrotating steel ball is held in a vertically mounted chuck and, using an applied load, is forced against an axially mounted steel rotating ring. The test ring is rotated at a fixed speed while being partially immersed in a lubricant reservoir. This maintains the ring in a wet condition and continuously transports a lubricating film of test fluid to the ball and ring interface. The diameter of the wear scar generated on the test ball is used as a measure of the fluid’s lubricating properties.

The apparatus can be used by adjusting the operating conditions to reproduce two different wear mechanisms. Therefore, the ALTE can assess a lubricant’s performance in that regard. These mechanisms are described below.