| 摘要 |
A spiral coil shaped insertion body is composed of a cylinder portion having a fixed outside diameter and a taper portion having an outside diameter gradually reduced from the cylinder portion toward its distal end. The outside thread pitch diameter of the cylinder portion is greater than the pitch diameter of the female screw, and the inside thread pitch diameter of a region of the taper portion covering one or more turns is smaller than the pitch diameter of a male screw. The distal end of the taper portion may be extended directly to form a small-diameter cylinder portion.
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