Screw member

A threaded fastening assembly comprising:

• a bolt, a nut, a fixing pin, and a positioning piece;
• wherein the bolt includes a head, a shank connected to a bottom surface of the head, at least one first groove arranged axially on a cylindrical surface of the shank, and at least one first threaded segment disposed on a part of the cylindrical surface without the first groove;
• the first threaded segment is provided with a plurality of first crests and a plurality of first roots;
• wherein the nut is provided with at least one second groove disposed axially on an inner cylindrical surface of the nut and at least one second threaded segment arranged at a part of the inner cylindrical surface without the second groove;
• the second threaded segment which includes a plurality of second crests and a plurality of second roots is mated and threaded with the first threaded segment while the first groove and the second groove are aligned and combined with each other to form a locking space;
• wherein the fixing pin is a cylindrical rod used for being mounted into the locking space;
• and
• wherein the positioning piece includes a first side, a second side, and a third side;
• two ends of the first side are connected to the second side and the third side correspondingly so that the positioning piece is in a horseshoe shape;
• an inner edge of the second side and an inner edge of the third side are facing and extending toward each other to form a convex portion respectively;
• the concave portions and the first grooves are matched;
• a distance between the inner edge of the second side and the inner edge of the third side facing each other is not only smaller than an outer diameter of the first crest of the first threaded segment, but also matching an inner diameter of the first root of the first threaded segment.