There are many different types of screws each with unique designs and functions. The most common types are concrete screws, wood screws, deck screws, and drywall screws.
What Are The Different Types of Screws?
Wood Screw
These screws usually have a partially-unthreaded shank. Usage involves attaching pieces of wood together (timber, plywood, etc.).
Concrete Screw
Stainless steel or carbon steel screws used to fasten materials to concrete.
Masonry Screw
Most masonry screws have a blue coating and fit into a pilot hole.
Double-ended (dowel) Screw
These screws have no head. Instead, they have two pointed ends. Often use is for joining two pieces of wood together.
Drive Screw
These screws have smooth and round heads that look like mushrooms. The shank has a reduced diameter.
Drywall Screw
These screws have a black phosphate coat and a bugle head. Often used to attach drywall to wood or metal studs.
Eye Bolt
Eye bolts attach wires to the surface of a building. They are loop-headed and function as an attachment point.
Decking Screw
These are long screws used to fasten deck boards.
Lag Screw/bolt
A heavy-duty fastener.
Chipboard Screw
Most chipboard screws are wax-coated. Used to fasten clipboard flooring.
Mirror Screw
The head of a mirror screw is decorative or covered.
Twinfast Screw
These screws are two-threaded which allows it to be drilled twice as fast.
Security Head Screw
The head of a security screw is irreversible. Used to secure vaults, safes, etc.
Machine Screws
Machine screws are a blend between a small bolt and a screw. Used to fasten metal to metal, or metal to plastic.
Socket Screws
Socket screws have a cylindrical head. In most cases, these screws join metal to metal. Used on items often disassembled and reassembled over time.
Sheet Metal Screws
Sheet metal screws fasten two pieces of sheet metal together. Sometimes used connect sheet metal to other types of metal, such as tubing. These screws often have a round head, flat head, or a hex head.
Types of Screw Heads
Countersunk Screw Head
A countersunk screw is a type of fastening that lies flat with the surface of the material it holds. You can cover the head with a screw cap or piece of wood.
Flat Screw Head
Most have stainless steel or zinc coating. Flat head screws sink into the material leaving very little of the head exposed.
Raised Screw Head
A raised screw head is a cross between a countersunk and a round head. The top is round but tapers towards the shank. Raised heads are the go-to choice for a more decorative finish.
Bugle
Bugle screws are self-drillings screws used for drywall installations. The countersunk head has a flat top and a concave under-head surface.
Binder Screw Head
Binder head screws or binding head screws are like pan heads but much thicker with a deeper slot. Binder head screws have a 10% larger bearing surface than pan head screws.
Domed Head Screw
A domed head screw sits above the surface of the material. Screws such as pan, button, binding, and truss head screws all have domed heads.
Flange
Flange head screws have a circular rim under the head that helps to distribute the load.
Truss Head Screw
Truss head screws are extra wide with a somewhat rounded surface or top. The head or top of the screw protrudes above the surface. It occupies a wider surface area under the head.
Screw Head Drive Types
Hex External
These types of screws have a hexagonal shaped head that protrudes the surface of the material that you insert them into. Typically, you’ll need a socket or wrench to insert or remove these screws.
Hex Internal
The various screw heads that we call hex internal need an Allen wrench to install them. They’re common screws that come with furniture that requires some sort of assembly. The Allen wrench is usually a part of the package as well.
Phillips
If you were wondering what is the most common screw head then the Phillips screw head sits on top of the list.
A Phillips drive is characterized by a cross-shaped recess with rounded edges at the cross-sections.
Pozidriv
A Pozidriv screw head looks similar to a Phillips but the Pozidriv has fewer grooves and is more star-shaped. On the Pozidriv, you’ll notice ribs between each of the four arms, and they’ll be marked with a “pz.”
Quadrex
The quadrex has a Phillips-like design but the middle of the cross shape is squared rather than pointed.
Slotted
When you think of a slot head screw you probably assume that its a flat head screw. That’s because, on the head, there’s one narrow opening for a flat screwdriver.
It’s one of the most common type of screws and, by design, they strip. But, they only strip to prevent us from over-tightening them.
Square Recess
If you’ve ever heard the term Robertson then you already know a bit about square recess screws (they’re the same thing).
The bit that drives square recess screws also juts out on a square taper because these screws have a square centered point that prevents cam outs.
Star
There are many different styles of star headed screws. For example, a double-square drive has two Robertson’s squares that form an 8-point star in the middle. On the other hand, there is a triple square with three Robertson’s squares, creating a 12-point star.
TORX
TORX screw bits are part of most drill sets but you probably never used them. TORX screws are 6-point star-shaped and you see them in electronic devices like gaming consoles and computers.
TORX Plus
TORX Plus screws have shallower groves than regular TORX screws. Therefore, you can use a bit more force when drilling them into place.
TRI-Wing
The tri-wing, also known as triangular slotted, is a screw with three slotted “wings” and a small triangular hole in the center. Unlike the “tri-point” fastener, the slots are offset and do not intersect the center of the fastener.
References
- http://screwsnutsbolts.wix.com/screwsnutsbolts
- NASA-RP-1228 Fastener Design Manual – http://hdl.handle.net/2060/19900009424
- Imperial/Metric fastening sizes comparison – http://www.baconsdozen.co.uk/tools/conversion%20charts.htm