A drill bushing for a drill unit. In one embodiment, the drill bushing includes a base member having an upper surface, a lower surface configured to rest on a workpiece having a pilot hole, and a retaining member that projects from the lower surface of the base member. The retaining member has a cylindrical outer diameter that fits within the pilot hole. The drill bushing further includes a drill hole that passes from the upper surface of the base member through the retaining member to provide a passage for a drill bit. The drill bushing further includes an expandable slit that passes through the base member and the retaining member to the drill hole, and an adjustment member configured to expand the expandable slit to increase the cylindrical outer diameter of the retaining member within the pilot hole.