Abstract
Bowers and Zisman have postulated a simple expression relating the friction coefficient of thin solid lubricant films to the shear strength of the film material and the contact pressure involved. They have attempted to demonstrate the validity of this expression by comparing shear strength and friction measurements made using two types of experimental configurations. It is argued here that the measurements compared are intrinsically equivalent and will yield equivalent results even when the friction mechanism is such that the postulated equation is not valid. Hence, the comparisons made do not in any way test the validity of the postulated equation.