Either the pin or the disc can be wear- and friction-tested using the pin on disc tester. The pin is usually a sphere however it may be any geometry that simulates the actual application counter surface.
A load cell attached to the pin on disc tester is used to measure the evolution of the friction coefficient with sliding distance. Sliding wear of the disc can be measured after the pin on disc test using a simple piece of equipment called a Calo tester.
The pin on disc test has proved particularly useful in providing a simple wear and friction test for low friction coatings on machine components, such as the valve train, particularly in motor sports. These components are now coated with low friction coatings such as diamond-like carbon to reduce energy losses and the requirement for lubricant.