Self-tapping screws work by drilling their own hole in an object or tapping their own threads in a hole. They are classified as either self-drilling or thread cutting screws. They are used most commonly in sheet metal applications, but can be found in plastics and wood as well. There are a variety of screws made to fit any application. A self-tapping screw is ideal for projects where you do not have access to both sides of the materials you are fastening or when the items being mated may have to be taken apart later.
Drill a pilot hole through the objects being fastened with your drill. The drill bit needs to be smaller than the outside diameter of the threads on the screw you are using, otherwise the threads will have nothing to tap into.
Position the screw in the pilot hole so that it is straight up and down. Going in on an angle can cause the screw head to strip.
Turn the screw to the right using a either a flat head or Philips screwdriver.
Tighten the screw until it becomes difficult to move or will no longer turn.
Fastener stores or your local hardware store can help you select the correct screw for your application. To determine the type of screwdriver needed, look at the screw head. A Phillips screw has a star shape, while a flat head is one straight line.
Wear safety glasses when drilling.