Csk Self Tapping Screw Steel BZP with an AB point and a flat CSk head – they create their own thread in the material when turned without need of pre-drilling. For use on sheet metal and other malleable materials. An HSS drill bit will be needed to drill a pilot hole. The diameter of this holes will vary according to the thickness of the material you are self tapping into Gauge Drill size4 2.0mm-2.5mm6 2.5mm-3.2mm8 3.0mm-3.5mm10 3.5mm-4.2mm12 4.5mm-5.0mm14 4.9mm-5.8mm