Types of Screws for Every Construction Project
Nov 09, 2020
Three types of fasteners are ubiquitous in construction: nails, screws, and bolts (paired with their partners, nuts).
Threads are the most obvious difference that distinguishes nails from screws, and what helps make screws the perfect fastener for many situations where tensile strength and holding power are your primary concerns.
“As they thread their way through the fibers, instead of pushing them out, they’re sneaking in between them. When I try to pull it out, now I have fiber sitting directly on top of this thread.” -Jordan Smith
While threads are common to all screws and they give screws their holding power, there are still many different types of screws, with thread and head designs best suited for certain tasks or materials.
Screws can be described by their drive types, which is the space where a screwdriver or a drill bit is placed in the screw head to install (or remove) it.
Flat Head Screws
A flat head screw, which has a single slot across the center of the head, was long the common design of most screws. When a screw is being installed manually, a single groove generally functions well, but put too much pressure on it or attempt to use a high-power drill, and it is easy to slip out of the groove. (“Cam out” or “camming out” refers to a screwdriver or a drill bit slipping out of the groove of a screw—it’s something to avoid as it can damage both the screw and the bit, as well as the material where you are installing the screw.)
Phillips Head Screws
These screws with a signature cross on their heads were invented in the1930s. Whether you are using a screwdriver or a drill, you are less likely to slip than with a single slot groove, making it easier to install them. As power tools have become more common, Phillips head screws (and variations on it) have become increasingly popular. In many buildings, single-slot screws are reserved for those places where the screw head will be visible like plate covers around light switches.
These screws build on the pluses of the Philips head and instead of having a cross shape on its head, a 6-sided star-shaped indentation further decreases the possibility of slipping. The design also makes it easier to remove than is true of a Philips head screw. To use them, however, you’ll need a star driver.
Square Head or Robertson Screws
With a small square indented in the head of the screw, this is another design intended to minimize the risk of camming out. The “Robertson” in the screw’s name is after its Canadian inventor—they continue to be especially popular in Canada and are also often used in building boats, where their tendency not to slip is invaluable.
Hex or Allen Screws
These screws have a hexagon in the middle of their heads (thus the name “hex head”) and you’ll need Allen wrenches to install them. They are best suited for situations where you expect that you will have to remove the screws and reassemble the structure—that is why you are more likely to come across hexagonal heads in an order from Ikea than at a construction site.
Why don’t structures fall down or come apart? Learn all about the stuff that holds building materials together in the MT Copeland online Fasteners and Adhesives course. Taught by professional builder Jordan Smith, the course covers topics ranging from nails and screws to glues and epoxies.