# Coefficient of Friction

The mathematical relationship of the frictional forces present between two objects in sliding contact, or how easily one object will slide against another. The coefficient of friction can be expressed as the maximum frictional force that acts just as relative motion is initiated divided by the force with which the two bodies in contact are pressed together in a direction perpendicular to their contacting surfaces. The higher the coefficient of friction, the greater the frictional forces that exist. In practical printing application where friction itself is important (such as in the minimization of abrasion and wear between moving surfaces), the coefficient of friction is not likely to need to be known specifically, although the lowering of the coefficient of friction is desirable. The use of lubricants (which can be liquids such as oils, greases, and waxes, or solids such as the surface roughness of a gravure cylinder, for example) acts to lower the coefficient of friction. (See Friction.)