The present paper includes an analysis of individual differences among observers in subjective surface roughness and an examination of usefulness of the sensory measurement. Eighteen test pieces were prepared from turned workpieces of freecutting brass (BsBM) in which Rrms (3 levels) Mean spacing of profile irregularities (3 levels) and radius of profile peaks (2 levels) were factorially combined. Four groups of 212 people in consideration of their experience in work participated in the experiments. For purpose of the present study, essential pairs required to classify the subjects into some types were selected from among all of the possible pairs of test pieces. Each subject was instructed to rate both visually and tactually the surface roughness of the test pieces on a five-point scale using the paired comparison method. The results of subject's judgments of the pairs imply the type of individual subjects. According to obtained results, the subjects may be classified into three types: [Rrms type]; subject who judges surface roughness under the influence of Rrms, [Pitch type]; subject who judges surface roughness under the influence of mean spacing and [other type]; subject who judges surface roughness from complicated information or not to have enough judging ability within the range of physical features of the test pieces.

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