The roughness profile was obtained using the envelope line from the primary profile. The peaks in roughness profile were defined as the portions above the envelope line moved downward to a certain height. Though the width of combined motifs (the third step above) is recommended to be no more than 500 µm, it should be defined with considering the characteristics of the tactile sense of finger. For determining this width, the sensory test consisting of paired comparison made out. Specimens were prepared by photoengraving with PVAC (Poly vinyl acetate) resin on silk screen and have parallel grooves with the same land width. The grooves were 0.1, 0.5 mm in width, and 8, 12, 15, 20, 50, 80 µm in depth for specimens of series A, and 0.1, 0.2,.0.25, 0.5, 1.0 mm in width, and 8, 20 µm in depth for series B. Specimens of series A and B were for determining the effect of depth and width of grooves on tactile roughness, respectively. Subjects wearing an eye mask moved their index fingers back and forth on the surfaces across a pair of specimens and identified which was rougher. The pairs of specimens were chosen randomly from among all of the specimens, and the subjects judged the roughness of each possible pair. The tactile roughness was estimated statistically from the sensory test.
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