Surface roughness changes according to the insert runout. As the feedrate in lowered, both the maximum surface roughness value and the arithmetic mean surface roughness value decrease in all cases. As shown in Figs. 7 and 8, in some ranges of the federate, the cutter with severe runouts gives better surface roughness than one with mild runouts. Over these ranges, however, the cutter with severe runout has the worse surface roughness. This means that the surface roughness should be controlled by the surface roughness model, considering the insert runouts.