Abstract: A device for radial machining and welding of a tubular body, said device comprising a tool support which can be placed around the tubular body and including four rollers assuring its guiding in rotation. The support comprises a main body of relatively massive shape which can receive, in its central part, a machining tool or welding tool, and to which are fastened two guide rollers. The guide rollers are placed on both sides of the axis of symmetry of the tool support. Two guide carriages are provided, on each of which guide carriage is mounted a guide roller, and means are provided to modify the position of the guide carriages in relation to the body as a function of the diameter of the tubular body.