Tube fitting

In a tube fitting comprising:

• at least one cylindrically-shaped ferrule with a tapered end and an abutment end;
• a body part having an externally threaded cylindrical extension and an internal channel terminating at the end of the extension in a frustroconically-shaped mouth which engages the tapered end of said ferrule;
• and a nut having a wall with an internally threaded portion for engaging the threaded extension of said body part and an abutment means, said wall defining a cavity containing said ferrule and, said ferrule and said nut having channels running through them with axes concentric with the axis of the channel in the extension of said body;
• the improvement wherein said nut comprises two movably interconnected parts, a first nut part, as described above, and a second nut part comprising a thin tubular portion passing through the channel in said first nut part into the cavity, the end of said thin tubular portion which extends into the cavity being radially flared and being disposed in abutting engagement with the abutment means of said first nut part, the flare having a diameter greater than the diameter of the channel in said first nut part but less than the diameter of the cavity in said first nut part, thereby preventing dissociation of the two nut parts while allowing rotation of the first nut part relative to the second nut part around the axis of the channels in said nut parts, the flared end of the thin tubular portion being in locking contact with the abutment end of said ferrule and the end of the thin tubular portion, opposite said flared end, being provided with tool engaging means thereon.