The traction is generated between an upper specimen (ball or barrel) in contact against a rotating disc. The upper specimen can be either rotating or stationary.
MTM Traction Disc
This is a disposable, highly polished steel disc, and during the test, the ball is loaded onto its polished upper surface. It is attached to the vertical driveshaft in the lubricant pot.
This is a super finished AISI 52100 (535A99) test ball. The highly polished surface finish of the ball plays an important role in the repeatability of test results and in reducing disc wear during each test. Each ball should be used only once. The balls are supplied with a drilled hole to allow them to be attached to the ball drive stub shaft for the traction measurements. The test ball can be interchanged with alternative upper specimens.