Abstract: An expandable fixed dummy block is provided for fixing on the end of a stem of an extrusion press. The dummy block has a longitudinally extending axis of symmetry and outer wall, a base having a central cavity symmetrical about the axis symmetry, and a mandrel symmetrical about the longitudinal axis for sitting in the cavity in the base and being free to rotate in the cavity. The cavity is defined by an endless side wall sloping radially inwardly from its mouth away from the outer wall to a bottom and the mandrel has a face and side wall sloping radially inwardly from the edge of the mandrel to a rear seat and having an outer edge bevelled so as not to extend beyond the inner radial dimensions of the mouth of the cavity. The angle of the side wall defining the cavity to the axis of symmetry is less than the angle of the side wall of the mandrel to the axis of symmetry.