Nippon Kokan Kabushiki Kaisha

Masaru Okamura

Takeo Yamada

Mitsuaki Uesugi

A method and an apparatus for detecting a flaw on threads of a male screw, which comprises: fully applying a light from a light source onto tops, roots and flanks of threads of a male screw while rotating the male screw around the axis thereof; continuously measuring, by means of a photoelectric converter, electric signal values corresponding to variations in brightness of the male screw in the axial direction thereof during one turn of the male screw around the axis thereof; moving-averaging the thus measured electric signal values corresponding to the variations in brightness of the male screw in the axial direction thereof; determining electric signal values corresponding to variations in brightness of the male screw in the circumferential direction thereof, on the basis of the thus moving-averaged electric signal values corresponding to the variations in brightness of the male screw in the axial direction thereof; obtaining a mean square value of the thus determined electric signal values corresponding to the variations in brightness of the male screw in the circumferential direction thereof; and comparing the thus obtained mean square value with a previously set reference value to detect a flaw on the threads of the male screw.

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Kawasaki, Japan

Masaru Okamura