Surprisingly, if two metal surfaces are polished until they are extremely smooth, the coefficient of friction will actually increase. Recent experiments show that friction doesn’t depend on surface roughness at the atomic scale! Friction is usually caused by chemical bonds between atoms on the two surfaces, but the fundamental causes of surface friction are still a problem that is not totally solved.

One method is to use surfaces that have less ability to form chemical bonds. Teflon is one such surface. Another is to have a thin film of oil between the surfaces. The oil will prevent bonding of the atoms in one surface with those of the other. Oil or other lubricants can reduce the coefficient of friction to about 0.1 to 0.2.