Abstract: A device for grooving the internal surface of tubes is disclosed as including a holding die for holding in position inside the tube a floating chuck equipped with a grooved chuck and a grooving unit including a rotating cage for retaining a number of rotating balls for compressing the tube wall against the grooved chuck to form a groove in the tube. The grooving unit includes a finishing die. The rotating cage includes a supporting member of which the internal profile, in an axial section is an arc of a circle, and a cage closure plate for retaining the balls in the cage and further includes a lubricator for the interior of the cage.