Screw head and tool for use therewith

A system for driving a screw, comprising:

• a screw;
• and
• a corresponding tool,
• wherein the screw includes a screw head comprising:
• a hexalobular slot in the upper surface of the screw head,
• an upper peripheral wall of hexalobular planform extending down into the screw head, the upper peripheral wall being parallel or near parallel to the axis of the screw,
• a sloping transition surface extending downwardly and inwardly with respect to the lower edge of the upper peripheral wall, and
• a tapered recess extending downwardly from the lower edge of the sloping transition surface, and
• wherein the dimensions of the screw head are such that when the screw head is engaged by the tool, which has upper and lower engagement sections and in which the upper engagement section fits within a recess formed in the hexalobular slot, there is an interference fit between the surface of the tapered recess and the external surface of the lower engagement section, and there is no engagement with the sloping transition surface.