Lapping is a low-velocity abrading finishing process that removes controlled, very small amounts of material. It is accomplished with loose abrasive grains between a tolling plate or wheel (called the lap) and the work surface to be finished.

Lapping is generally a final finishing operation that results in four major refinements in the workpiece:

• extreme accuracy of dimension
• correction of minor imperfections of shape
• refinement of surface finish
• close fit between mating surfaces

Less heat is generated than in most other finishing operations, thus minimizing the possibility of rehardened and decarburized areas on hardened or heat-treated parts. Typical applications include reference surfaces and air bearings for inspection systems, microlithography equipment, scientific and medical instruments, and sealing surfaces.