Self tapping screws are normally used with sheet metal and plastics. These have a countersunk head AKA flat head with a pozi (cross recessed) drive. They are typically used in conjunction with a countersunk hole providing a flush, snag free fit. As the name suggests, this type of screw forms its own thread as it is installed into a pre-drilled hole. Not to be confused with self drilling screws, the main difference is that self-tapping screws cannot go through metal without a pilot hole, which must be pre-drilled or pre-punched. Self-tappers are good for use with metals, various types of plastics (plywood, fiberglass, polycarbonates), and cast or forged material, like iron, aluminium, brass or bronze. Self-tapping screws also work for surfaces where you can’t secure the rear end with a nut. Common applications include fastening aluminium sections, attaching metal brackets onto wood, or inserting screws into plastic housings. This set contains a selection of of No.4, No.6 and No.8 (3.5mm, 4.2mm & 4.8mm thread diameter) screws. A2-70 stainless steel, also known as 304 or 18/8 grade has great weather resistance and longevity. It can be used in all outdoor conditions apart from where consistent exposure to either salt water or sewerage is expected.
