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In this report, the Vickers impression is investigated on the flatness of its pyramid surface and the figure on the specimen surface. Steel and brass are used for a specimen to be tested The pyramid surfaces are always convex and there is the highest point at the center. The figure of the impression on a specimen surface is curved inward on the hardened steel, while outward on the hard brass.(A) The pyramid surface is convex and higher at the center than the corner. The figure of the impression is inward curved, owing to the difference of the height between center and corner on the pyramid surface near the surface of specimen.(B) The surface of specimen is more swelled at the center between the corners of the impression than at the corner. The figure is outward curved, owing to the swelling difference.As the result, the figure is curved outward or inward, according to the mutual effect between the height difference in the pyramid surface and the swelling on the specimen surface.

It is very difficult to measure the thread pitch and angle in the nut. In this report, the plastic material such as Cu amalgam and dental wax is casted in the nut to obtain a casting for the nut. Its pitch and angle are easily measured, because the casting has external thread. The coefficient of thermal expansion of the dental wax is measured and the aging effect of Cu. amalgam is researched in order to research the source of the error for this measurement. As the result, Cu amalgam is preferable to the dental wax for the measurement of the nut.