Device in and connecting piece for a square tube assembly, and a fixture for manufacturing the device.

摘要

For connecting one square tube to another square tube or like element, there is provided a circumferentially incomplete inner thread which occupies at least two opposite partial areas 10 of the inner sides of two of the walls of the square tube which are of substantially equal thickness. The inner thread leaves the outer surfaces of said walls unaffected and is arranged for engaging a substantially cylindrical connecting piece (16,18) (27,28). The connecting piece has an external thread corresponding to the internal thread and is connectible to another square tube or like element. A fixture for making the inner thread in a simple manner has a body 38 and at least two side members 39 projecting therefrom for fixing the body 38 on a square tube. The body 38 has a through bore with an internal thread for guiding a screw tap for cutting the desired internal thread in the square tube.