Dumbell-like shaped symmetrical bidirectional tapered thread connection pair

A dumbbell-like shaped symmetrical bidirectional tapered thread connection pair, comprising an external thread (9) and an internal thread (6) in mutual thread fit, wherein:

• a complete unit thread of the dumbbell-like shaped symmetrical bidirectional tapered thread (1) is a helical dumbbell-like shaped symmetrical bidirectional tapered body small in the middle and large in both ends and comprising a bidirectional tapered hole (41) and/or a bidirectional truncated cone body (71);
• a thread body of the internal thread (6) is the helical bidirectional tapered hole (41) on an inner surface of a cylindrical body (2), and exists in a form of a “non-entity space”;
• a thread body of the external thread (9) is the helical bidirectional truncated cone body (71) on an outer surface of a columnar body (3), and exists in a form of a “material entity”;
• a left taper (95) is formed on a left conical surface of the symmetrical bidirectional tapered body and corresponds to a first taper angle (α1), and a right taper (96) is formed on a right conical surface of the symmetrical bidirectional tapered body and corresponds to a second taper angle (α2);
• the left taper (95) and the right taper (96) have opposite directions, and same and/or approximately same tapers;
• and
• the internal thread (6) and the external thread (9) contain the bidirectional truncated cone body by the bidirectional tapered hole till an inner conical surface of the bidirectional tapered hole and an outer conical surface of the bidirectional truncated cone body bear each other.