Abstract: The invention relates to a device for truncating tubes, comprising at least one knife, which cooperates at the end of the cut with a counter-knife positioned within the tube to be truncated and which is connected mechanically to a core of strong magnetic permeability. In one embodiment, a winding is wound in a framework around the tube to be truncated, to create a magnetic field in the core through the tube to be truncated so as to be able to act magnetically on the longitudinal position of the core and thus on that of the counter-knife. At least one pair of tubular sleeves are fitted at each of the ends of the framework and are formed of a material of strong magnetic permeability, to direct and form the lines of induction. In another embodiment, the winding is arranged around a core which is fixed with respect to said winding and whose axis is positioned parallel and at a distance from the longitudinal axis of the tube to be truncated.