How Do You Use Self-tapping Screws?

By: HowStuffWorks.com Contributors  | 

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.

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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.

Originally Published: May 31, 2011

Self-tapping Screws FAQs

What is a self-tapping screw used for?
As the name implies, self-tapping screws drill their own "little tunnels" by cutting precise threads when they are screwed into wood, plastic or metal. They are useful for products that you need to maintain regularly where you need to dissemble and reassemble the item along the same threads. A simple hand-held screwdriver can be used to drill a self-tapping screw.
Do you need a drill for self-tapping screws?
No, self-tapping screws can simply be inserted with either a screwdriver. However, it’s better to drill a small pilot hole before the you drill the screw.
How much weight can a self-tapping screw hold?
Typically, a self-tapping screw can sustain around 80 to 100 pounds of weight. However, this depends on various factors such as the type of threads on the screw, its length, screw quality, screw insertion angle and forces that act on it.
Can you use self-tapping screws in aluminum?
Self-tapping screws are very versatile and can be used fasten metals together, including aluminum.
Do self-tapping screws come loose?
Since self-tapping screws may be used multiple times, they can come loose if the hole becomes too big.

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