Picking a screw for a wood project used to be as easy as deciding if you wanted to use a zinc or brass screw. But over the years, improvements in technology has led to a lot of different screw types.
No need to worry though – this post will help you find the perfect screw.
Wood screws can be made from a variety of materials including brass, bronze, aluminium etc.
However, the most common material for wood screws is steel, which is used a lot because it’s strong, cheap and easy to find.
So is steel a good choice? Well old-fashioned tapered steel screws can be a pain to use.
In fact, many woodworkers switched to using drywall screws when they became common a few decades ago.
These are made from harder steel than the standard steel tapered screws. This means they can be driven in quickly without pre-drilled pilot holes.
This makes drywall screws a good choice for a lot of projects. However, they’re quite brittle, meaning that they’ll snap when subjected to high stresses. So don’t use them for projects that needs strong construction.
But it’s not all bad news. A new type of screw – production screws – was invented.
Production screws have points and threads that are sharp enough and strong enough to penetrate even hardwoods and some metals. And they’re strong enough to withstand the high torque delivered by a power drill or impact driver.
So production screws are ideally suited to most woodworking projects.
The most common brands are GRK Fasteners™, SPAX®, PowerPro™ and Saber Drive™.
If you’re working on an indoor project, steel screws are fine.
However, these will rust if used outdoors or in an atmosphere with high humidity.
In those cases, deck screws are a great choice. They’re basically production screws that have been plated or coated to improve their resistance to rust. The best deck screws are made from silicon bronze or stainless steel.
If you need even greater corrosion resistance, grade 305 or grade 316 stainless are resistant to salt and highly corrosive environments.
Apart from the material that a screw is made of, the shape of it’s head can have a big impact on how well it works for a project.
Head designs fall into two categories – flush and proud.
(image courtesy of Wonkee Donkee Tools)
Flush heads will sit sit flush with the work surface, leaving it relatively flat. Whereas proud heads leave a pronounced bump on the surface.
Trim head screws and bugle head screws are types of flush heads that are designed to sink into everything but the hardest woods.
Trim head screws are a good choice when you don’t want the head to show too much and are worried about splitting thin or delicate wood. Because of that, they’re a good choice for projects like mounting trim and moldings or for setting door jambs. However, they only have medium holding power.
If you need a flush screw with a lot of holding power, go for a bugle head. (It’s called a bugle head because the head sorta looks like a bugle 🙂 )
(image of bugle head screw. Courtesy of Home Depot.)
For traditional flush screws to sit flush with the surface, you have to drill countersink holes. This give the head of the screw a recess to sit in.
Production screws solve this problem by being self-countersinking. This means that they create their own recess as you drive them in. Which is another benefit of them.
There are even production screws made to self-countersink with delicate materials like veneered plywoods and melamine.
Common types of proud head screws include fillister head, round head, pan head and cheese head. These usually have a small head with a flat underside that rests against the wood.
(Image of a round head screw courtesy of Lowes.)
These will have a medium amount of hold with hardwoods. But they shouldn’t be used with softer woods as they tend to crush the wood near the surface.
And if the two pieces of wood you screwed together are ever stressed, the screw’s hold will be reduced even further.
Really, if you need to use a proud head screw, it’s usually best to use one with a large head. This increase contact with the wood and reduces crushing (and pull-through).
Mushroom head screws (AKA truss head screws) have a head that looks like a pan head screw but is much wider and flatter. These are a good choice if you’re mounting hardware on wood and don’t want a flush screw.
(image of a truss head screw courtesy of Home Depot.)
Washer head and super washer head screws are good when using a power driver. They look like regular screws but with a washer underneath the head. These are good when two pieces of wood need to be joined but you need to be able to adjust them later.
Traditional slotted screws have fallen out of favor because they tend to slip off the screwdriver, which leads to accidents and damage.
They also have a tendency to “cam out”. Camming out is when a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount.
And slipping or camming out happens even more often with power drivers. So as they became more popular, slotted screws lost favor.
Instead, many woodworkers now use Phillips head screws. These hit the scene in the 1930s and are popular because the criss-cross grooves automatically center the tip of the screwdriver.
(image of phillips head screw courtesy of Home Depot.)
Phillips head are less susceptible to camming out than slotted screws but it can still happen – especially with power drivers. (This can be avoided by carefully setting the clutch on your driver).
Recently, two drive types have started gaining popularity – TORX® and Robertson square drives.
(image of TORX head screw courtesy of ali express.)
These became popular for two reason – stick fit and resistance to camming out.
Stick fit is the ability for a screw and the driver to form a temporary connection. Basically, you can put a TORX or Robertson screw on the end of your driver and it will stay there while you drive it into place. This means that you don’t have to hold the screw while driving. Because of this, they make one-person jobs much easier.
Camming out is reduced by both TORX and Robertson by the fact that they both have deep recesses. This stops the driver head from slipping out. Another benefit is that they reduce driver wear because they need very little pressure to stay engaged.
TORX screws have a distinctive six pointed star-shaped head. These were originally used for vehicles and electronics. But over the last few years, they have started gaining popularity among woodworkers – especially as deck screws and cabinet screws.
Robertson square heads have a square head are less common but you can still find them in some hardware stores.
Another up and coming head type is from Outlaw Fasteners. They invented a three-tiered hexagonal head with 18 points of contact. This makes the head super sticky with almost no camming out. Outlaw Fasteners raised $100,000 via a Kickstarter and so far seem to be doing well.
Traditional tapered wood screws need a pilot hole when driven into anything but the softest woods. That because of their dull points.
That can be kind of a pain when driving a lot of screws because you have to do twice as much work – drill the pilot hole and then drive the screw.
Production screws fixed this by using a sharp point that bites into the wood, which pulls the screw down quickly.
Most production screws use a Type 17 auger point to do this. These are sharp and have a self-tapping flute which cuts a hole in the wood while channeling the debris up the shank of the screw.
(image of type 17 auger point courtesy of Home Depot)
Once the point of the screw has done it’s job of getting of pulling the screw into the wood, the thread has to continue that.
Back in the day, expert opinion was that you need coarse-threaded screws for softwoods, plywood, MDF etc. And you need fine-threaded screws for hardwoods.
But just as with screw heads and drive types, there have been some technological advances in the last few years which has called that advice into question.
The best advice I can give you is to read the instructions that come with the screws to see if they are suitable for your project.
Platings and Coatings
As I said earlier, steel screws will rust if used outdoors or in areas of high humidity (like near a shower).
To solve this problem, you can use steel screws that have been coated.
The coating prevents rust, reduces friction and also makes them look cool.
The most common plating on screws is bright zinc. This is largely decorative and doesn’t provide much rust resistance. Eventually these screws will corrode and develop what looks like white rust.
To avoid this, construction use bright golden zinc which provides much better corrosion resistance.
You’ll also see screws that are plated with black oxide (AKA black phosphorous). These look cool but don’t offer much resistance to rust. I’d avoid them.
Really, galvanizing gives you the best rust protection.
After the screw is made, the screw is coated with zinc using one of two methods.
Electroplating costs the screw with zinc by dunking the screw in a bath of zinc/saline and then running a current through it.
Hot-dipping covers the screw with zinc by dunking it in a bath of molten zinc.
Recently though, high-tech solutions have given galvanizing a run for it’s money. Blue-Kote™, NoCoRode PLUS, Climatek™ and epoxy coated screws are worth looking at if you don’t like the look of galvanized screws.
(image of Blue-Kote screw courtesy of Home Depot)
That’s a lot of info about screws!
Did you expect to learn so much about screws?
Well hopefully you weren’t overwhelmed 🙂
Overall, I’d boil it down to these rules:
1. Phillips head is better than slotted head. TORX and Robertson are better than Phillips.
2. Production screws are better than drywall screws (unless you’re handing drywall)
3. Use galvanized screws (or coated ones) outside.