Expansion nut for T-joint of pipes

A one-piece expansion nut for a T-joint of pipes, comprising:

• an expansion nut body defining an internal thread hole at a center thereof, the body including a plurality of long expanding pieces and short expanding pieces alternatively disposed around an outer periphery of the body wherein outer diameters formed by said long and short expanding pieces are the same, and the outer diameter is slightly larger than an inner diameter of a first pipe to be jointed, such that when said expansion nut is placed into the first pipe and a bolt is passed through a second pipe to screw into the internal thread hole for the T-joint, the long and short expanding pieces are respectively expanded to exert force against an inner wall of the first pipe in two stages, so as to firmly hold the expansion nut in place, wherein each long expanding piece includes a catch tab punched from an inner side of an upper part thereof, wherein an outer diameter formed by said catch tabs is slightly smaller than the outer diameters of said long or short expanding pieces;
• whereby when said long and short expanding pieces are respectively expanded to exert force against the inner wall of said first pipe, said catch tabs on said long expanding pieces are expanded to exert another force against the inner wall of said first pipe.