A self-tapping screw is designed to form its own threads as you drive it into a material such as wood, plastic or metal. In the past, you had to drill a guide hole before driving in whatever kind of screw would be used. Self-tapping screws create their own hole as pressure is exerted on them. They also provide a close, tight grip and a degree of certainty that the hole and screw fit exactly.
Self-tapping screws sound simple, but the science behind them is complex, and the choices within the realm of self-tapping screws are astounding. Within the self-tapping screw family are members that cut threads and others that form threads.
A self-tapping thread-forming screw would typically be used in plastic, and it deforms the material as it enters and drives inward.
A self-tapping thread-cutting screw would typically be used in wood or metal, and it cuts material out of its way as it enters and drives inward.
Self-tapping screws are normally made either from carbon steel or stainless steel, but they have other qualities that change their appearance and chemical composition. Stainless is the most commonly found screw material, often chosen for its corrosion resistance and is made with varying strengths that depend on the amount of nickel, chromium and other alloys they contain.
A screw well-fitted to the job not only means efficiency and quality but also durability and long life. Some people may ask: “How do you use self-tapping screws?” The answer is simple. They’re used like any other screw, where the user drives them in with a drill, screwdriver or machine.
The science behind the turn of self-tapping screws is extensive and involves multiple factors:
• Coating (If Any): Screws may be coated with polish, with nickel, copper, zinc or tin plating, with phosphate, oxide lacquer and possibly other materials depending on the purpose they’re serving and the finish and performance that’s expected.
• Color: Surface treatments on self-tapping screws cater to an array of uses since they come in a rainbow of colors such as yellow, blue, green, gray, black, silver, copper and extra-bright hues.
• Composition: Some engineering calculations are necessary to determine the correct alloy mix that achieves the desired hardness of many kinds of self-tapping screws.
• Diameter: When it comes down to holding something in place, the girth of a screw plays a key role. The self-tapping screw diameter should be matched to the job, whether light or heavy.
• Hardness/Strength: Similar to the composition of self-tapping screws is the heat treatment that tempers the screws to the desired hardness. The amount, duration and temperature of the heat all make a difference in the end product.
• Head Style: The head refers to the shape of the screw’s top, which may be round, oval, square, flat, socket, fillister or hexagonal.
• Length: People are probably most familiar with this characteristic of a self-tapping or another kind of screw. The length of the screw makes all the difference in whether it can reach and dig into its target without going too deep.
• Recess: The recess is the part of the screw that receives the screwdriver or drill. It can have a variety of shapes such as square, slot, Phillips and hex.
• Thread: Self-tapping screws do their work by way of the size, density and pattern of the thread on them. All of the thread’s elements, from how closely together the thread sits to how many rows of it there are and where they begin and end, play a huge role in the science of the turn.
• Tip: The point of a screw holds a lot of potential to penetrate the material, tap a proper hole and hold fast. Screw tips may range from having a fine, sharp shape to a blunt edge.
Self-tapping screws may have a range of these characteristics, most likely to match one of the many applications for which self-tapping screws are used. They use these characteristics to complete the essential work of holding other larger pieces in place. The following are just a few of the possible applications for self-tapping screws.
• Gutters: Self-tapping screws are usually the foundation of any gutter-attachment system. They make for less work, a secure hold and a finish that will withstand a beating from the water and rooftop debris. The right screws will hold the gutters in place, withstand weather, resist corrosion, look neat and not drive too deeply, among other things.
• Medical: We don’t think of our bodies as a place where screws would go, but that’s exactly what happens in any number of replacements and other kinds of repair surgery. Medical articles routinely mention self-tapping screws and expound on their functionality for fastening parts inside the body. For example, dental implants that attach by screwing into the jaw bone are big, self-tapping screws with a tooth or teeth on top.
• Roofs: Self-tapping screws make the shingle and framing work go smoothly and can be ordered for whatever type of roofing materials you might use. Asphalt, wood and metal each have properties to which the screw can be matched for maximum grab, hold and endurance.
• Drywall: Hanging drywall is another place where self-tapping screws excel because of their threads. The pattern is designed to dig itself in tightly and hold fast, and the length penetrates whatever thickness of drywall is chosen. The right screws can make the difference between walls that hang straight, look good and last, and ones that don’t.
• Sheet Metal: The driving action and special drill-like tip of self-tapping screws are needed to work with various metals of different thicknesses. The screws might be used for anything from a barn roof and automobile to building construction and artwork.
• Plastic: The technology associated with self-tapping screws for plastic has evolved to the point that the pieces are now specialized and sometimes made of plastic themselves. Self-tapping screw technology has evolved to include more lightweight materials such as plastic and aluminum and shorter thread engagements.
The American Society of Civil Engineers did some testing with cross-laminated timber, which is growing in popularity. It found self-tapping screws to be sufficient for creating shear joints and bearing vertical loads associated with three-ply and five-ply laminate.
The following are just a few examples of the many industries that regularly use self-tapping screws.
There are millions of kinds of fasteners, and knowing the best type to use is a point of quality and a boost to businesses. There are similarities and differences between self-tapping, self-piercing and self-drilling screws. The thread, head and tip distinguish one from the other, as well as the intended use of the fastener.
Self-tapping screws are known for their ability to drill their own hole as they go along, as opposed to drilling a pilot hole like with flat-ended screws. They can have a sharp or blunt tip. A sharp tip is usually for drilling into softer materials, such as wood or plastic, without having to drill a pilot hole. The blunt tip helps your success rate when drilling into something harder, like metal.
Self-tappers are often used in sheet-metal applications where one-sided access is an issue. This might be applicable in automotive, aviation and other industries. The technology has overcome what used to be a challenge for many industries — fastening together thin metal safely with a screw. Self-tapping screws are used for a wide range of applications involving steel and aluminum, as well as alloys and mixed applications. They handle metal gauges from about 24 through 30.
Self-drilling screws have a fluted tip, almost like a drill bit, to dig into the material before its threads drive through it. You will also see and hear these called Tek® screws, pro points and drill-bit screws. They also come with a variety of options for the head, tip and other characteristics. The self-drilling screws are what you need to penetrate thicker metal such as 22 gauge.
Self-drilling screws are used for many metal applications but weren’t intended to go from metal to wood. For that, there is a specialty self-drilling screw called the Tek reamer. Most of the time, it is this type of screw that makes the deck-to-building connection in a deck-construction project. These types of screws have tips numbered one through five, which refers to the thickness of the metal it can penetrate without a pilot hole.
Self-piercing screws feature an ability to pierce light-gauge metal and as they’re driven, tap their mating threads. They have a sharp angle of about 30 degrees and are considered a high-strength fastener. You will regularly see and hear self-piercing screws referred to as zip, needle- or pencil-point screws, as well as self-tapping screws.
In fact, it isn’t unusual for all the terms to be used and mixed interchangeably for any screw-type fastener that doesn’t have a flat bottom, despite the differences among them. The three types described here work in similar ways, and some specialty screws have twin or dual characteristics and functions.
The American Society for Testing and Materials (ASTM) conducts analyses of self-tapping screws to be sure the science for the turn is correct. The tests ensure the screws are being manufactured to established standards and will perform as expected. These standards test the screws’ following qualities:
• Assembly tension
• Corrosion resistance, which entails a salt-spray test
• Drill capacity, drive and hole size
• Hydrogen embrittlement
• Plating/coating thickness
• Torsional strength
You can easily browse our expansive inventory of different types of screws and other fasteners to find what you want, and you can always contact us for help. All Points specializes in ceramic, stainless, copper, zinc and other types of screws that are self-tapping, self-drilling, self-piercing and any combinations of these. We also have a wide variety of sizes available.
To pluck a few examples, we carry screws for many specialized and everyday uses:
• Drywall Tek self-drilling screws in six sizes, a black-oxide finish and quantities that range from 3,500 to 10,000 cases.
• Hex washer head drill points self-drilling screws in a few dozen sizes with zinc-tipped steel composition and the option for painted heads.
• Phillips flat-, pancake- and wafer-head self-drilling screws in zinc-plated steel.
• Ceramic-coated self-piercing screws for gutters, siding, carports, barns and roofs.
• Phillips and slotted sheet-metal self-tapping screws in several dozen sizes and made of steel with many options for coating.
• Deck screws in self-tapping, piercing and drilling including flatheads, ceramic coating, bugle heads, square drivers, options for cedar and fasteners formulated to resist salt spray.
• Woodworking screws include versions for particle board, different wood hardness, front-facing wood and hinges, with black-phosphate and yellow-zinc finishes.
Consider All Points an expert partner you can consult anytime about the science of the turn. We’re here to listen, talk and provide any needed guidance. As seasoned veterans in our field and professionals who take pride in our work, we’re known for being able to find hard-to-find items.
Besides expertise in self-tapping, self-piercing and self-drilling screws, All Points also offers rivets, anchors, nuts, bolts, nails, washers, drill bits, cable ties, reciprocal saw blades and other products to help you fasten whatever it is your business requires. We’re happy to provide free samples and quotes, and we’re able to accommodate large-quantity orders quickly.
All Points is a nationwide distributor with years of experience that will benefit you and your business as you navigate the options and select the fastener that best fits your needs.