Abstract: A threaded bush having a cylindrical body provided with a female thread in an inner surface, a male thread in an outer surface, a plurality of triangular recessed stop grooves spaced equally in a lower sloping-down portion, each stop recessed groove formed with a vertical side wall and a curved side wall defining a small angle, the curved side wills guiding and cutting in a wall of a hole which this bush is to be screwed in, the vertical side wall cutting positively the wall of the hole, the triangular recessed stop grooves engaging uncut wall material of the hole to prevent this bush from loosening out of the hole.