Joinery Systems
To me, there are joinery systems, and there are traditional joints. A joinery system, like the domino, or dowels, is a system that uses a jig or a specific tool that makes a sort of ‘universal’ joint. Traditional joints, like the mortise and tenon or the dovetail, use universal tools or machines to create a joint for a specific scenario.
I wanted to find an easy way to decide which joinery system to use, between pocket screws, biscuits, dominos, and dowels, while giving objective numbers to back it all up, so that you can rest easy knowing your furniture projects will last.
Pocket Screws
Pocket screws are kiboshed by many woodworkers, but they’re used in many professional applications and can definitely do the job if used appropriately. Are they as strong as some other systems or traditional joints? No, definitely not, but that shouldn’t deter you from using them.
Pocket screws are an easy way to get started joining wood if you’re a beginner. It’s one of the less expensive systems you can buy into, and it will work in many joinery situations. Smaller, clamp-on jigs can be finicky and move around while you’re drilling. But a larger, stationary jig is only about a hundred dollars and makes a world of a difference, including allowing you to work faster.
An advantage of pocket holes is that you don’t need to wait for glue to dry to continue working. I’m not saying you don’t need glue–far from it, but pocket screws will hold everything just fine until the glue dries.
All the same, I would be selective about where and when to use pocket screws. You can’t always conceal them, like in case joinery, so they end up on the outside, which is not a good look. But they do work for drawer boxes where the front will conceal them. They do just fine in situations where there isn’t much stress on them, like built-in plywood cabinetry, or when I needed to put a divider in the drawer cabinet in my workbench. But if you’re using pocket screws to attach aprons to table legs for a kitchen table, don’t go all Coyote Ugly on it.
You know the old cost, time, strength triangle? I place pocket screws here, because although they’re not necessarily stronger, they’re inexpensive, and very fast. These are broad generalizations for the big picture.
But how fast are they? Well, I made five joints using two and three quarter inch poplar, and timed how long it took me to drill the pocket holes, and screw them together. I removed the highest and lowest values, averaged out the middle three, and the result was fifty-seven seconds per joint. Seems pretty fast to me, but we’ll see how they compare with the other joinery systems soon.
My final verdict with pocket screws is that they’re good for getting started in woodworking, and in specific situations where the utmost strength is not required. But they can’t be guaranteed to stand up to the test of time in many places in stand-alone furniture builds.
Biscuits
I’m just gonna go ahead and say it–I think biscuits are kinda whatever. A biscuit is essentially a spline that goes into a slot that’s cut by a small saw blade that you plunge into the joint. The biscuit itself is inexpensive, but the joiner is gonna run you at least a couple hundred dollars.
Biscuits are pretty darn wide, and even the smallest one cuts a slot that is 2 inches wide, and that size biscuit doesn’t give you much holding power at all. The more common number twenty biscuit cuts an enormous three inch wide slot, so as you can already tell, the biscuit joiner isn’t going to work for everything.
Another thing that bugs me about biscuits is the inconsistent fit they have. The slots are all the same thickness, but the biscuit itself can vary and is usually pretty loose. One bit of conventional wisdom that gets tossed around is that the biscuit is supposed to swell and create a tight fit, but that simply hasn’t been my experience. More often than not, I’m fiddling around with lining up the joint after gluing, while trying to clamp it tight. This is especially frustrating when I’ve used biscuits specifically for aligning panel glue-ups.
The biscuit joiner itself is very simple to operate. You just have a fence height setting, and a plunge depth setting. You essentially just have to point and shoot, which makes it a pretty fast operation. How fast? One minute and thirty-three seconds on average - which is thirty-six seconds slower than pocket holes. And then you’ll have to wait for the glue to dry. However, when I’m willing to wait the extra time, I’m usually after something that will give me stronger results.
So how strong are these joints? Well, I did some testing. I had my test joint glued together with biscuits clamped up in a way that a bottle jack put pressure on the joint, and I measured the force with a bathroom scale underneath. This is not very precise, but it still gives a decent idea of how they compare.
I did the test five times total, removed the highest and lowest values, and got an average result of 68.7 pounds for the biscuited joint. What does that mean? The same test for the pocket hole joint with glue got an average of 86.3 pounds–that’s 17.6 pounds stronger. So pocket hole screws are stronger than biscuits…to be honest, I was a little surprised by that.
Granted, this is only one type of joint, seeing as you can join two boards together in a number of different orientations. Furthermore, this radial or racking direction is not the only way a joint can be stressed, but it is quite common.
So biscuit, I place thee here in the cost, time, strength triangle, but honestly, I can’t recommend the biscuit joiner over pocket screws for most applications. If you want fast but half-decent alignment on panel glue-ups, it’ll do the job, but for everything else, I would favour most of the other options, as you’ll see in a minute.
Domino
Probably the number one question from people who have never used the next joinery system is, do I need a Festool domino, and is it worth it? I know you all either love these things, or love to hate them. Why all the fuss? Well, the Festool domino has pretty much the same form factor and function as a biscuit joiner for about five times the price.
In regards to function, the domino can join two pieces of wood just like a biscuit joiner, and that’s where the similarities end. The domino joiner cuts a mortise up to 10mm thick into two pieces of wood so you can glue them together with a domino, otherwise known as a floating tenon, loose tenon, or slip tenon. Which is by and large a mortise and tenon, the bread and butter of all woodworking joinery for probably thousands of years.
So if you can make a mortise and tenon with a router and table saw, or hand tools, do you need a domino? You don’t, but it does makes things go a lot faster. Plus, you can use a domino to join wood together in any orientation, whether it be frames, boxes, cases, miters, angled joinery, it all works. And since the domino plunges a much narrower and thicker mortise than a biscuit joiner makes a slot, it’s more flexible and stronger.
I did the same strength test with the same size joint using two six millimeter dominos and got an average of 147.7 pounds. I used 6 millimeter because it’s approximately one third the thickness of the material, which is the prevailing popular opinion on how thick a tenon should be. I used two dominos where I could only use one biscuit because, that’s what I would do if this were a real-life joint. If I compared one domino to one biscuit to one pocket screw to one dowel, I would definitely get different numbers, but they would be meaningless in a real-world scenario. So because of this, the domino was slightly slower than the biscuit joiner at an average of one minute and fifty-five seconds, even though they have the same form factor.But yeah, you pay a price for it. Like I said, the tool itself is about 5 times the price of your average biscuit joiner, and the dominos themselves are also around two to five times more expensive than biscuits. But if the price doesn’t faze you, then here’s another consideration before you buy: if you are a results-driven woodworker, then get the domino and that will get you to the finish line faster. If you are more of a fan of the process than the final result, the domino might not interest you, and that’s okay.
So yeah, it is expensive, but to some it’s worth the expense because of how strong and fast it is, particularly in a professional environment. All the same, the Festool domino goes here on the cost, time, strength triangle.
Dowels
Dowels are super common in crappy Ikea furniture, which is why I think they get a bad rep from woodworkers. Factory flat-pack furniture is usually made from particle board or at best a very soft wood, and you’re not instructed to glue the dowels in when assembling, so of course it falls apart.
There are a lot of bad dowel jigs out there. They cause misalignments and the dowels end up very loose fitting. However, if you invest in a high-quality dowel jig, it can quickly become a favourite tool to use and is truly a thing of beauty. The one that I have experience with, and you’ve seen me use it before on the channel, is the dowelmax. Yes, it’s expensive for a dowel jig, but you can trust me on this ‘cause I’ve had a couple of cheaper jigs that are a hundred dollars or less, and they are worse than miserable to use. I’d rather use pocket screws. A good jig is still a fraction of the price of a domino, and it’ll work in any scenario that a domino can–which is a lot of scenarios.
Most of the joinery on my workbench build was done with dowels, using some massive half inch by four inch dowels. My bench is a tank, and hasn’t budged since I finished it. I’ve also used dowels in case joinery like my drill charging station, and in many drawer boxes that have lasted for years. You can also do exposed dowels, something that I don’t recommend doing with dominos, because that would look pretty yikes in my opinion.
For my test, I was able to put four three-eighths inch dowels in the same sized joint as I was able to fit two 6 millimeter dominos, or just the one biscuit. If you compare one domino to one dowel, I’d hedge a bet that the domino is stronger. But you can fit many more dowels in a same sized joint than you would if you were using dominos. Remember that the domino averaged 147.7 pounds? Well the dowel averaged 171.7 pounds. This actually shouldn’t be too surprising as there’s more surface area in four dowels than in these two dominos.
And speed? The whole jig with a drill does seem to be a bit slower, and unsurprisingly, it is. I averaged two minutes and twenty-five seconds per joint, which is half a minute slower than the domino. These dowel jigs can be adjusted so they can work in a variety of ways, and that causes the set up time to be longer for this than simply adjusting the fence and depth on the domino. Even still, I truly believe the dowel jig is reasonable for the average home hobbyist woodworker.
Where does the dowel jig lie on my triangle? Right about here.
There are a bunch of other joinery systems, but I wanted to talk about the four most popular ones. There’s Rockler’s Beadlock system, which looks great, but the end result is similar to a domino and you achieve it much like a dowel jig. JessEm looks to be releasing the very cool looking Pocket Mill Pro soon, which seems like a dowel jig but can route a mortise with a drill. That too will give you a similar result to a domino in the time of a dowel jig.
Strength Versus Longevity
I know I’ve been throwing out a bunch of numbers out, and I don’t like to think in terms of ‘how strong is this joint’ because that will lead me down the road of grading them from worst to best and choosing the strongest joint every single time. Instead, I ask myself: How long do I want this to last?
Don’t feel like you have to go down the road of traditional mortise and tenons and dovetails just because some magazine told you that it’s unacceptable if your furniture lasts anything less than a hundred years. However, if that’s how you get your groove on in the shop, then have at ‘er.
Final Thoughts
So what does all this mean? The joinery system that strikes the best balance between cost, time and strength is dowels. The domino is strong enough for most things, but it’s expensive. Pocket screws are inexpensive and fast, but might not be great for every situation. And biscuits…well, I’ve come to the realization that I don’t think I have room in my shop for the biscuit joiner anymore.
I learned that if I want fast joinery, pocket screws are faster and a little bit stronger to boot. If I want alignment, I can use the dowel jig to do that, or I guess I have the domino now too. And to any new woodworkers out there, the pocket screw does make sense for an easy start, and investing in a high-quality dowel jig later on will serve you and your furniture for years.