A square baler including a baling chamber having a floor formed of spaced profiles, side walls and a top wall, and a density belt surrounding the baling chamber. The density belt is formed of a U-shaped frame having three beams welded to one another to define a floor beam for supporting the floor of the baling chamber and two upright beams for supporting the side walls of the baling chamber and a tensioning rod releasably secured to the upper ends of the two upright beams to prevent the upright beams from splaying apart.