Abstract: Screwdriver provided with a flat blade tip to engage a diametral slot in a screw head and a central guide spigot of square or other non-circular cross section for engagement in an axial guide bore of the screw head, is also provided with a pair of buttresses projecting radially on each side of the tip for abutment or close alignment with the head on each side of the slot. The bit may consist of an axial insert including the spigot and buttresses which is secured in a cross-slot of the blade tip, and the spigot is preferably slightly tapered, and in some applications may extend axially beyond the blade tip.