ühikuta (normaalpingest sõltumatu) suurus - haardehõõrdumise esilekutsumiseks vajaliku kontaktnihkepinge ja tooriku materjali voolepiiri jagatis (vt haardehõõrdumine; vrd hõõrdetegur), interface friction coefficient for which the interface shear stress is taken to be proportional to the flow stress; the proportionality facor is called interface shear factor (or friction shear factor) and is usually denoted as m; the friction shear factor takes on values between 0 (perfect lubrication) and 1 (sticking friction) during metalworking (see: sticking friction; compare: coefficient of friction)