Variations in power during disk grinding have been explained and equations developed to represent the power in terms of the grinding variables. It has been shown that depth of cut is below the critical magnitude so that ultimate shear strength of the metal is involved for all but the initial 30 to 120 seconds of grinding. It has also been shown that the coefficient of friction is higher against stainless steel than against mild steel, and that the basic differences in performance and mechanism on these two metals originate in this property. Photomicrographs of microflats are shown. The mechanism of microdressing is explained in terms of thermal shock and mechanical impact in relation to the effect of applied load upon grinding efficiency.