Screws are one of the most widely used types of fasteners, designed to hold objects together by creating a strong mechanical grip. Unlike bolts, screws typically engage directly with the material they are inserted into, using their helical threads to convert rotational motion into linear motion and clamping force. They can be used in wood, metal, plastic, and other materials, making them versatile tools for construction, manufacturing, and everyday household use.
Screws come in many shapes, sizes, and thread types, each suited for specific applications. Common varieties include wood screws, machine screws, sheet metal screws, and self-tapping screws. The design of the threads, point, and head determines how the screw penetrates the material, holds the load, and resists loosening. Some screws are intended for permanent fastening, while others allow for disassembly and reuse.
The head of a screw determines how it is driven and the type of tool required. Flat head, pan head, round head, and hex head are common designs, each providing different levels of flushness, holding strength, and aesthetic finish. Screw heads are typically driven using screwdrivers, Allen keys, or power tools, which makes installation quick and efficient.
Screws are essential in applications where precise alignment, secure fastening, and high load resistance are needed. They are commonly used in furniture assembly, cabinetry, machinery, electronics, automotive components, and construction projects. The choice of material, coating, and thread type can help screws resist corrosion, wear, and vibration, extending the longevity of the joint.
Types of Screws and Their Uses
By Head Type
Flat Head Screws
Flat head screws are one of the most widely used screw types in woodworking, cabinetry, and general construction. What makes them distinctive is their countersunk design — the underside of the head is angled (usually at 82° in the US or 90° in metric standards), which allows the head to sit perfectly flush with or even slightly below the surface of the material.
This is especially important in applications where a protruding screw head would be a safety hazard, interfere with other components, or simply look unattractive.
Pan Head Screws
Pan head screws have a flat-bottomed, slightly rounded top with vertical sides — resembling an upside-down pan, which is where the name comes from. Unlike flat head screws, they don’t countersink into the material; instead, they sit on top of the surface. The wide, flat bearing surface under the head distributes clamping force over a larger area, which reduces the risk of the screw pulling through soft or thin materials.
Pan head screws are extremely common in electronics, sheet metal work, plastic enclosures, and light machinery.
Round Head Screws
Round head screws have a dome-shaped head that curves smoothly upward and sits entirely above the surface of the material. They were once the most popular screw type in woodworking and general manufacturing, but they’ve largely been replaced by pan head screws in modern applications because pan heads offer a lower profile and better bearing surface.
However, round head screws are still found in older furniture, antique restorations, and certain decorative applications where the rounded, classic look is desirable.
Oval Head Screws
Oval head screws are something of a middle ground between flat and round head designs. Like flat heads, they have a countersunk bottom that allows them to sit partially recessed into the material. But unlike flat heads, the top of the head has a gentle dome or oval curve rather than being completely flat. This gives them a more finished, decorative appearance while still allowing them to sit fairly close to the surface.
They are commonly used in applications where aesthetics matter but a fully flush finish isn’t strictly necessary — things like door hinges, cabinet hardware, face plates, and decorative trim.
Truss Head Screws
Truss head screws have an unusually wide, low-profile dome head — wider than any other common screw head type relative to the screw’s shaft diameter. This wide head is specifically designed to spread the clamping load across a very large area, which makes them ideal for use with soft or thin materials that might otherwise be pulled through by a smaller head under load.
They’re heavily used in HVAC ductwork, metal roofing, and sheet metal assembly where the material being fastened is thin-gauge steel that could deform under a concentrated load. The wide head also makes them a good choice for fastening sheet goods like plywood, OSB, or thin panels where you want to avoid pull-through.
Bugle Head Screws
Bugle head screws look similar to flat head screws at first glance, but there’s a critical difference in the geometry of the underside of the head. While a flat head has a straight, conical taper, a bugle head has a curved, trumpet-like concave taper beneath the head. This design is specifically engineered for drywall installation, which is why you’ll almost never see a bugle head screw used for anything else.
Here’s why the curve matters: when driving a screw into drywall, you’re fastening through a layer of paper, then gypsum, then more paper. If you use a flat head screw, the sharp angle of the cone can cut and tear the paper face of the drywall, which weakens the hold and can create a failed anchor point.
The curved bugle shape, by contrast, gently compresses and dimples the drywall paper without cutting it, leaving the paper fibers intact and the drywall surface undamaged. This small design detail makes a significant difference in the structural integrity of a drywall installation.
Hex Head Screws
Hex head screws feature a six-sided head that is driven using a wrench, socket, or nut driver rather than a screwdriver. This design allows for the application of very high torque, which is why hex head screws are the go-to choice for heavy structural applications, automotive assembly, machinery, and any situation requiring a very strong, reliable fastener.
The six-sided geometry gives you six points of engagement with the driving tool, distributing the rotational force evenly and making it very difficult for the tool to slip. This is a significant advantage over slotted or even Phillips drives when applying the high levels of torque needed for structural fastening.
Button Head Screws
Button head screws have a low, rounded dome head with a socket drive (almost always hex/Allen or Torx) recessed into the top. The head profile is low and compact, giving them a clean, finished appearance while still providing enough bearing surface for secure fastening. They’re a popular choice in applications where the screw will be visible and aesthetics matter, but where a standard socket cap screw would look too industrial.
You’ll find button head screws on bicycle components, motorcycle accessories, custom automotive builds, consumer electronics, and precision mechanical equipment. They’re also popular in fabricated metal furniture and industrial design products where a sleek, modern look is desired.
Socket Head Cap Screws
Socket head cap screws, often simply called “cap screws,” have a tall, cylindrical head with a precisely machined hexagonal socket in the top. They’re designed for high-strength applications in precision machinery, tooling, and engineering components.
The tall cylindrical head allows for a deep hex socket, which means a hex key (Allen wrench) can engage deeply and transmit very high torque without slipping or stripping.
Cheese Head Screws
Cheese head screws have a thick, cylindrical head with vertical sides and a flat top — a profile that resembles a round block of cheese, hence the name. The head is deeper than a pan head, which allows for a deeper, more substantial drive slot, giving better tool engagement and reducing the chance of the driver slipping. This makes them particularly useful in applications where precise torque control matters.
They’re more common in European engineering and manufacturing than in North American applications, and you’ll often find them in electrical equipment, instrumentation panels, scientific apparatus, and mechanical assemblies where the fasteners are accessed regularly for maintenance.
Fillister Head Screws
Fillister head screws have a small-diameter, tall cylindrical head with steep, nearly vertical sides and a flat top. Because the head diameter is relatively small in proportion to its height, they can fit into tight counterbores and recesses that other screw heads couldn’t access. The head height also allows for a very deep drive recess, providing excellent driver engagement and torque transfer.
They’re used in precision mechanical assemblies, scientific instruments, and fine machinery where space is tight and the screws need to seat in counterbored holes without the head protruding.
Flange Head Screws
Flange head screws have an integrated circular flange — essentially a built-in washer — that is part of the head itself rather than a separate component. This flange increases the bearing surface area significantly compared to a standard hex head or pan head, which distributes the clamping force more evenly and reduces the likelihood of the screw loosening under vibration.
The serrated or smooth underside of the flange also provides a locking effect against the mating surface, which is why flange head screws are widely used in automotive applications — particularly for attaching exhaust components, engine brackets, and suspension parts that are subject to constant vibration.
By Drive Type
Phillips Head Screws
The Phillips drive was invented by Henry F. Phillips in the 1930s and patented with the goal of enabling power-tool driving on automobile assembly lines. The cross-shaped recess in the head is designed to allow the driver bit to cam out — or slip out of the recess — when a certain torque level is reached. This was actually intentional in the original design, as it prevented over-tightening on automobile assembly lines where consistent torque was important.
Today, Phillips head screws are the single most common drive type in the world. They’re found in virtually every industry and every country. However, the cam-out tendency that was once considered a feature is now widely seen as a drawback, especially in high-torque applications where a stripped Phillips recess is a common frustration.
Slotted Screws
Slotted screws are the oldest screw drive type, featuring a single straight groove across the head into which a flat-blade screwdriver fits. They predate all other drive systems and were the dominant screw type for centuries before the Phillips drive emerged in the 1930s. Despite being largely superseded in construction and manufacturing, slotted screws are still widely used today for specific reasons.
In electrical work, slotted screws are standard on terminal blocks, switch plates, and outlet covers because electricians can use the blade of a flathead screwdriver to both drive the screw and handle wiring tasks with the same tool. In plumbing, they appear on many fittings and access panels.
Torx (Star) Screws
Torx screws were developed by Camcar Textron in 1967 and feature a six-pointed star-shaped drive recess. The geometry of the Torx drive is fundamentally different from Phillips or slotted in that it is specifically designed to resist cam-out. The vertical walls of the star points transfer torque directly through the drive, so the driver stays engaged even under very high torque levels without riding up and out of the recess.
This makes Torx screws the preferred choice in automotive manufacturing, electronics assembly, and any application requiring high torque or repeated fastening and removal cycles.
Pozidriv Screws
Pozidriv screws look similar to Phillips at first glance, but they have additional radial lines between the four main cross arms — a secondary cross at 45 degrees to the primary one. This additional geometry dramatically reduces the cam-out tendency of the drive, allowing much higher torque to be applied before the driver slips. Pozidriv screws and drivers are not interchangeable with Phillips — using a Phillips driver in a Pozidriv recess (or vice versa) results in poor engagement and rapid stripping.
Pozidriv screws are standard in European construction, cabinetry, and manufacturing, and if you’re working with flat-pack furniture from European manufacturers or doing construction work with European-sourced materials, you’ll encounter them regularly.
Robertson (Square) Screws
Robertson screws have a square recess in the head and were invented by Canadian Peter Lymburne Robertson in 1908, making them one of the earliest improvements over the slotted drive. The square socket provides four solid walls of engagement for the driver, virtually eliminating cam-out under normal driving conditions. This makes them extremely efficient for power-tool driving — the screw can even be loaded on the driver tip and held there by friction without falling off, which significantly speeds up production work.
Robertson screws are dominant in Canadian construction, woodworking, and cabinetry, and many Canadian tradespeople swear by them as superior to Phillips for everyday fastening. They’re less common in the United States and Europe, largely due to historical licensing disputes and institutional preferences for Phillips.
Hex Socket Screws (Allen/Hex Key Screws)
Hex socket screws use a six-sided internal recess that is driven with an Allen wrench (hex key) or hex bit. The drive is simple, strong, and highly resistant to stripping because the six flat walls of the hexagon transmit torque extremely efficiently.
Hex socket screws are among the most widely encountered fasteners in the world because of their use in flat-pack furniture (IKEA products famously use hex socket fasteners), machinery, bicycles, and countless other products.
The hex drive allows the fastener to be accessed from directly above using an L-shaped Allen wrench, or from various angles with a long-arm key.
Tri-Wing Screws
Tri-wing screws feature a distinctive three-winged recess that requires a specialized tri-wing driver for installation and removal. This unusual drive pattern makes them inherently tamper-resistant — a standard Phillips, Torx, or slotted driver won’t engage properly, making casual removal very difficult without the correct tool. They were designed specifically to discourage unauthorized servicing and disassembly.
Nintendo was one of the most prominent users of tri-wing screws, using them in Game Boys, the original Nintendo DS, Wii remotes, and various other handheld devices to prevent users from opening the devices without going through authorized repair channels. They’re also found in some aerospace applications, power tools, and consumer electronics.
Spanner (Snake Eye) Screws
Spanner screws, often called snake eye screws, have a drive recess consisting of two small, round holes positioned opposite each other in the head. A special spanner driver with two corresponding pins is required to drive or remove them. This is one of the most effective tamper-resistant drive types available because spanner drivers are genuinely rare and the head resists all common tools — standard screwdrivers, pliers, and drill bits can’t easily engage the two circular holes.
You’ll encounter spanner screws in public restrooms (particularly on toilet partitions and fixtures), on elevators and escalators, in public parks and playground equipment, and on street signs and public infrastructure — anywhere that vandalism or unauthorized tampering is a real concern.
Torx Plus Screws
Torx Plus is an enhanced version of the standard Torx drive developed to provide even better torque transfer and longer tool life. While standard Torx has pointed tips at the ends of each lobe, Torx Plus has a more rounded, elliptical lobe shape that increases the contact area between the driver and the recess. This increased contact area means the drive can handle higher torque levels before showing wear, and driver bits last significantly longer in high-volume production environments.
Torx Plus screws are used in aerospace manufacturing, medical devices, and high-performance automotive components where fastener reliability is absolutely critical.
One-Way Screws
One-way screws are an extreme tamper-resistant fastener that can be installed with a standard slotted screwdriver but cannot be removed with any conventional tool. The head recess is designed asymmetrically — the driver engages properly when rotated in the tightening direction, but when reverse rotation is attempted, the angled walls of the recess cause the driver to cam out immediately. The result is a screw that goes in easily but won’t come out through normal means.
These screws are used in applications where permanent fastening is a security requirement. They’re found on license plate frames in some jurisdictions, in correctional facilities and psychiatric institutions (where screws that could be removed and fashioned into tools or weapons are a genuine safety concern), in public vandal-prone areas, and in commercial products where unauthorized disassembly would create liability or safety issues.
By Application / Material
Wood Screws
Wood screws are specifically engineered for fastening into wood, and their design reflects the unique properties of wood as a material. A traditional wood screw has a partially threaded shank — the section near the head is smooth (unthreaded) while the lower portion near the tip is threaded with a coarse, widely spaced thread.
This design is intentional: the coarse thread bites aggressively into the lower piece of wood and pulls it toward the upper piece, while the smooth shank in the upper piece allows that piece to be pulled tight against the lower one without the thread binding in both pieces simultaneously.
Drywall Screws
Drywall screws are a specialized fastener designed with one purpose: to attach gypsum drywall panels to either wood or metal framing quickly, securely, and without damaging the paper surface of the drywall.
They’re slender, which minimizes splitting in wood studs, and they have a very sharp, needle-like point that penetrates drywall and bites into framing without requiring pre-drilling. The bugle-shaped head (as described earlier) is what allows them to seat in the drywall surface without tearing the paper.
Sheet Metal Screws
Sheet metal screws are fully threaded from tip to head — unlike wood screws, there is no smooth shank section. The threads are sharp and aggressive, designed to cut into and grip thin metal sheets.
They’re typically harder than wood screws to enable them to penetrate metal without a pre-threaded hole — the screw essentially taps its own thread as it’s driven in, though a pilot hole slightly smaller than the screw’s outer diameter is often recommended to make driving easier and prevent metal distortion.
Machine Screws
Machine screws are precision fasteners with uniform, machine-cut threads that run the full length of the screw shaft. Unlike wood or sheet metal screws, machine screws don’t cut their own threads — they require either a pre-threaded (tapped) hole in the mating component or a nut on the other side to function.
This precision threading allows for exact, repeatable torque specifications and makes machine screws ideal for any application where disassembly and reassembly are anticipated.
Self-Drilling Screws (Tek Screws)
Self-drilling screws, commonly called Tek screws (a brand name that has become generic), have a special drill-point tip that looks like a small twist drill bit. This tip allows the screw to drill its own pilot hole and tap its own thread in one simultaneous operation, eliminating the separate steps of drilling and tapping. This makes them extraordinarily efficient in production environments where thousands of metal-to-metal or metal-to-wood connections need to be made quickly.
Self-Tapping Screws
Self-tapping screws are related to self-drilling screws but are distinct in an important way — they tap (cut) their own thread into a pre-drilled pilot hole but do not drill the hole themselves. The tip is sharp and pointed but not a drill bit; a correctly sized pilot hole must be drilled first.
Once inserted into the pilot hole, the screw’s specially designed threads cut into the material as the screw is driven, forming their own mating thread without requiring a tap.
Self-tapping screws are widely used in plastics, die-cast metals, aluminum, and thin sheet metal. They’re common in the assembly of electronic housings, automotive interior trim panels, small appliances, and plumbing fixtures.
Lag Screws (Lag Bolts)
Lag screws, sometimes called lag bolts despite not technically being bolts, are heavy-duty fasteners designed for high-load wood connections. They have a hex head (driven with a wrench or socket, not a screwdriver), a coarse, aggressive wood-screw thread, and are available in much larger diameters and lengths than standard wood screws — commonly from 1/4″ to 3/4″ in diameter and from 1″ to 6″ or more in length. This large size gives them dramatically higher load capacity than standard screws.
Lag screws are used in structural wood connections throughout construction: attaching deck ledger boards to house rim joists, fastening stair stringers, connecting heavy timber framing members, mounting brackets to structural lumber, and securing large hardware like hinges, handles, and anchors.
Deck Screws
Deck screws are purpose-built for outdoor wood decking applications where moisture exposure, wood movement, and corrosion are constant challenges. They differ from standard wood screws in several important ways.
First, they’re coated or made from materials specifically chosen for corrosion resistance — options include hot-dipped galvanized steel, stainless steel (particularly important with certain tropical hardwoods that react with zinc), and polymer-coated screws. Standard zinc-plated screws will rust within one or two seasons in outdoor use, leaving rust stains on the decking.
Concrete Screws (Tapcon Screws)
Concrete screws, widely known by the brand name Tapcon, are hardened masonry fasteners that anchor directly into concrete, brick, or block without requiring plastic or lead anchors.
The screw is made from hardened carbon steel with a specially designed thread that cuts into the masonry material as the screw is driven in. The alternate high-low thread pattern creates a strong mechanical interlock with the masonry that resists pull-out forces effectively.
Drywall-to-Metal Screws
Drywall-to-metal screws are specifically designed for the increasingly common situation in commercial and multi-family residential construction where drywall is attached to steel stud framing rather than wood.
Standard coarse-thread drywall screws used for wood studs do not perform well in metal studs — their wide thread spacing doesn’t engage thin steel effectively and the screw can wobble or strip out. Fine-thread drywall-to-metal screws address this by having more closely spaced threads that grip the thin steel stud material reliably.
Roofing Screws
Roofing screws are specialized fasteners used to attach metal roofing panels, corrugated steel sheets, and metal roof flashing to structural framing. What distinguishes roofing screws from other sheet metal screws is the rubber or EPDM (ethylene propylene diene monomer) washer bonded to the underside of the hex flange head.
This washer is the key weatherproofing element — when the screw is driven to the correct depth, the washer compresses against the metal roofing surface and creates a waterproof seal around the screw hole, preventing water infiltration.
Particle Board Screws
Particle board screws are engineered specifically for use in particle board, MDF (medium-density fiberboard), and other manufactured wood composite panels. These materials present unique fastening challenges: they’re made from wood particles or fibers bonded together with resin, which gives them very different structural properties from solid wood or plywood.
Particle board is relatively weak in tension (pull-out), prone to crumbling around screw holes if over-driven, and has poor resistance to swelling and crumbling when wet.
Cabinet Screws
Cabinet screws are heavy-duty fasteners designed specifically for the demanding job of hanging kitchen and bathroom cabinets securely to wall studs.
The defining feature of most cabinet screws is a large washer head that provides a significantly larger bearing surface than standard screw heads — this is important because the wood at the top of a cabinet box needs to distribute the significant weight of the cabinet and its contents over as large an area as possible without cracking or pulling through.
Pocket Hole Screws
Pocket hole screws are specialized fasteners used exclusively in pocket hole joinery — a woodworking technique popularized by the Kreg jig system, in which an angled hole is drilled at the end of one board so that a screw can be driven at an angle into the adjacent board.
The geometry of this joint means the screw approaches the mating board at a steep angle rather than straight on, and the screw needs to be designed to handle this unusual loading condition effectively.
Structural Screws
Structural screws represent a major evolution in construction fastening technology. They are engineered and load-rated fasteners designed to replace traditional lag screws and bolts in structural wood applications — and they offer significant advantages.
While a lag screw requires pre-drilling a pilot hole and is driven slowly with a wrench or socket, structural screws like the Simpson Strong-Drive SDWS or the FastenMaster HeadLok can be driven directly into lumber with a standard impact driver without any pre-drilling in many applications, dramatically speeding up installation.
Masonry Screws
Masonry screws function similarly to concrete screws but are more broadly applied across the full range of masonry materials including concrete, brick, mortar joints, cinder block, and stone.
The principle is the same: a hardened screw with specialized cutting threads is driven into a pre-drilled pilot hole in the masonry, where it cuts its own mating thread and creates a strong mechanical anchor. No separate anchor or plug is needed, which simplifies installation significantly compared to traditional expansion anchors.
Chipboard Screws
Chipboard screws are versatile construction fasteners with a coarse, aggressive thread profile designed for use in chipboard (also called particle board), OSB (oriented strand board), plywood, and softwood lumber.
They’re one of the most commonly used screw types in European construction and increasingly popular worldwide. The coarse thread cuts aggressively through the fibrous material of composite wood panels, providing strong pull-out resistance despite the relatively weak matrix of these materials.
Hanger Bolts
Hanger bolts are a two-in-one fastener with no traditional head at all. One end has a wood screw thread (coarse, tapered) for anchoring into wood, and the other end has a machine screw thread (uniform, for accepting a nut). The middle portion is typically smooth or has a slight shoulder.
To install a hanger bolt, two nuts are threaded on the machine screw end and locked against each other, then a wrench is used to drive the wood screw end into the wood — once installed, the nuts are removed, leaving a threaded stud protruding from the wood surface.
Elevator Bolts
Elevator bolts have a very large, flat, thin head with a small square neck below the head. The large flat head is the defining feature — it provides an extremely large bearing surface and is designed specifically to sit flush with or slightly below the surface of the material it’s fastening, so that the fastener head doesn’t protrude above the surface and create an obstruction. The square neck prevents the bolt from spinning when a nut is tightened on the other side.
Eye Screws
Eye screws are simple but enormously useful fasteners that combine a wood screw thread with a closed circular loop (the “eye”) where a standard head would be. The loop provides an anchor point for hanging, connecting, or guiding — anything that needs to be tied, hooked, or attached to a fixed point.
They’re driven into wood by hand (for small sizes) or with a screwdriver or awl inserted through the eye as a lever (for larger sizes or denser wood).
Hook Screws
Hook screws are similar to eye screws in that they replace the traditional head with a functional shape — in this case, a J-shape or L-shape rather than a closed loop.
The open hook end allows items to be hung or removed without threading them through a closed eye, which makes hook screws much more convenient for applications where you’re regularly hanging and removing items. Like eye screws, they’re driven by hand into pre-started holes or by using a tool inserted into the hook as a lever.
Specialty and Unique Screw Types
Set Screws
Set screws are entirely headless fasteners — the entire screw is threaded, with no head protruding beyond the surface. They’re driven using a hex key (Allen wrench) inserted into a hex socket in the top of the screw, and they’re designed to be driven completely into a threaded hole until flush or below the surface.
The tip of the set screw (which can be flat, cone-shaped, cup-shaped, or dog-point style depending on the application) presses against the shaft or surface below to lock a component in place.
Thumb Screws
Thumb screws are fasteners designed to be installed and removed entirely by hand, without any tools. The head is enlarged and shaped for finger grip — either a flat, knurled disc shape or a butterfly/wing shape that provides excellent finger leverage.
The threaded shaft is standard machine thread that engages a tapped hole or nut. The defining feature is that no tool should ever be needed to operate them in their intended application.
Shoulder Screws (Stripper Bolts)
Shoulder screws have a unique three-part geometry: a socket head cap above, a precisely machined smooth cylindrical shoulder in the middle, and a shorter threaded section at the bottom. The shoulder — the smooth cylindrical section — is the functional part of the screw.
It is ground to very tight dimensional tolerances and a smooth surface finish, allowing it to serve as a precision pivot, guide pin, or bearing surface. The threaded end anchors the screw in the base component, and the head captures whatever component needs to rotate or slide on the shoulder.
Captive Screws
Captive screws are a clever solution to a common problem in panel and equipment design: the dropped screw. Standard screws, when removed from a panel or cover, are completely separate components that can be dropped, lost, or misplaced — in server rooms, aircraft, or industrial machinery, a dropped screw can cause serious damage to expensive equipment or create dangerous foreign object debris. Captive screws solve this by being mechanically retained in the panel even when fully loosened, so they can never fall out.
Grub Screws
Grub screws are essentially set screws by another name — the term “grub screw” is the British English designation for the same headless, fully-threaded fastener known as a set screw in North American usage.
The name reportedly comes from the grub-like appearance of the small, headless screw buried inside a component. Like set screws, they’re driven with a hex key and are used to lock components onto shafts in motors, gearboxes, and mechanical assemblies.
SEMS Screws
SEMS screws (the name comes from “pre-assembled” in a truncated form) are standard screws that come factory-assembled with a free-spinning washer already captured under the head.
The washer is assembled onto the screw shaft before the threads are rolled, which captures it permanently — the washer can spin freely and move slightly but cannot be removed. This pre-assembly eliminates the need to handle loose washers during installation and ensures the washer is always present and properly positioned.
Security Screws
Security screws are a broad category encompassing any fastener specifically designed to be difficult or impossible to remove without a special, proprietary tool. The goal is to prevent tampering, vandalism, theft, or unauthorized servicing.
While we’ve already covered specific security drive types like tri-wing, spanner, and one-way screws, the security screw category also includes several other designs: pin-in Torx (standard Torx with a hardened pin in the center of the recess that prevents standard Torx drivers from engaging), pin-in hex (same concept with a hex socket), and clutch head screws (a figure-eight shaped drive that can be tightened but not removed with a standard driver).
Thread-Forming Screws
Thread-forming screws, sometimes called cold-forming screws, work on a fundamentally different principle from thread-cutting screws. Instead of cutting away material to create threads (which produces chips or swarf), thread-forming screws displace the material around them as they advance, pressing the material into a thread form without removing any of it.
This plastic deformation actually cold-works the material, increasing its hardness and strength around the thread engagement zone and creating a very tight, secure mating thread.