An expansion head for expansion tools for hollow work-pieces, particularly for the ends of plastic pipes and metal-plastic composite pipes, comprising a union cap having a guide flange directed radially inward, and a set of expandable jaws of sector-shaped design, each received individually by an inner flange sector overlapping the guide flange so that they are radially movable in the union cap, wherein the set of sector-shaped expandable jaws is movable between a closed state and an expansion state, and in a closed state, an approximately cylindrical lateral area is formed by an envelope of the outer walls of the set of expandable jaws, wherein characterized in that each expandable jaw is provided with at least one recess extending in the direction of the longitudinal axis of the expandable jaws so that in a closed state of the expansion head, the surface of the outer walls of the set of expandable jaws corresponds to 25% to 75% of the surface of the envelope of the outer walls of the set of expandable jaws.