When you are looking for fasteners, you are trying to evaluate the situation and pick the best way to put materials together. Fastening one or more pieces of light, medium, or heavy gage sheet metal together may require the use of adhesives, riveting, or self-tapping screws. If an application requires access or several layers, tapping screws maybe the best option.
So here comes the question, what is a self-tapping screw? Tapping screws are designed to cut their own hole as it is screwed into the materials. This creates a good snug fit between the mating threads and also allows the parts to be reassembled if necessary.
Cuts its own thread while being driven into the mating material. It makes a small hole while entering the material which creates a tight friction fit between the threads. This helps fight vibration loosening and allows the parts to be taken apart if needed. Mostly used in 1-2-layer thin gage sheet metal applications.
Self-drilling vs self-tapping screw
A self-tapping screw can also be self-drilling. Basically a self-drilling screw is a tapping screw that doesn't need a pilot hole. They both technically tap their own threads, all screw do this to varying degrees. But, the self-drilling screws skip a step in the process. The way self-drilling screw are made make them ideal for metal. You can use them with wood they won't grip as well because they have wasted length with no thread. I hope we have cleared up all the confusion, just remember all self-drilling screws are self-tapping, but not all self-tapping screws are self-drilling.
How do you use a self-tapping screw
Self-tapping screws drill their own little tunnels by cutting precise threads when they are screwed into wood, plastic or metal. It's helpful to use self-tapping screws for products that you need to maintain regularly such as air-conditioning units or canopies where you need to dissemble and reassemble the item along the same threads. You can insert self-tapping screws with either a hand-held or electric screwdriver.
Before you use self-tapping screws, it's helpful, although not mandatory, to drill a pilot hole through the material. This ensures the screw will go in easily and will be positioned correctly. Make sure to use a smaller drill bit than the self-tapping screw itself when drilling the pilot hole. Otherwise, if the hole is too large, the screw threads won't have anything to attach to. Then position the screw straight and screw it in place with a flat head or Phillips screwdriver (depending on the screw head). If the screw goes in crooked, it could cause the head to strip. Next, tighten the screw until it no longer turns easily. Be careful not to over-tighten the screw because it could cause the threads to strip.
Self-tapping screws come with a sharp, piercing tip or a flat, blunt tip. The sharp-tipped screws are designed for drilling their own hole into softer materials such as wood and plastic so they don't need a pilot hole. The advantage of the flat-tipped screw is that it won't get stuck in the material and break off. When you're drilling into harder material such as sheet metal you need to drill a pilot hole in advance. For thicker metal, it may require more than one screw to drill through the surface. To save time and labor, you can use self-drilling self-tapping screws to drill into metal. Although these screws are more expensive, they're capable of drilling and fastening in one step.