what’s wrong with Domino joinery

[roger wiegand]

In 50-100 years we'll have a better idea of whether there are any issues with using dominos. I suspect, that just as with doweled joints, which dominos are a slight variant on, dominos make a good strong joint when new. We'll see how they stand up with a few decades of wood movement and as the glues start to fail. My suspicion, unsupported by data, is that like dowels and other loose tenons, they won't hold up as well as well-fitted M&T joints, which we know can last hundreds or thousands of years.

I don't expect to be around to learn the answer. If you're building things for short term use (a couple decades) you probably don't need to worry about it.

[Steve Rozmiarek]

I suspect the statement began as something like "For edge joining, dominos provide only alignment". In this case, as a glued edge butt joint is as strong as the wood in that weak direction, it's true.

In other uses, they are the same strength as a similarly sized standard mortise and tenon. If you replace a large tenon with multiple smaller dominos, it gets more complicated.

Exactly. I personally do not like the domino machine better than the other ways that I cut floating tenon, so I don't use it much.

[Stan Calow]

Only reason I don't have one is the cost.

[Charlie Jones]

I have used a biscuit joiner for many years. None of the furniture and cabinets I used it on have come apart. I am sure they would if someone pushed them apart with a hydraulic ram. Some of those tests going around are just silly. I recently bought a Domino. I have no reason to doubt it will be as good or even better. I know it is more versatile as I have used it a bunch already. A loose tenon is a loose tenon. I will still make them another way when the job requires it.

[Malcolm McLeod]

Some mortice cutters are fast or slow, some noisy or quiet, some cheap or expensive, some portable or 1200lb monsters. Setup times may vary wildly, but all simply leave a hole in the base material. The size, accuracy, and suitability of the resulting hole are largely up to the perpetrator - no matter the chosen cutter.

The Domino (machine) is just another mortice cutter. Period. The result is no different than any other mortice cutter, excepting perhaps the limitation of a hole with a rounded end. ...Exactly like a router or CNC?? And in each case, that end can be quickly squared up w/ a chisel if required. Usage still results in a hole.

And you can fill that hole with whatever you wish: integral or floating tenon, steel or balsa. You pick.

I find the Domino incredibly versatile and nothing 'wrong' with it. And rest assured , there are even more expensive options.

[Jim Becker]

Opinions are like, um...well...you know...that popular phrase that refers to anatomy. There's absolutely nothing wrong with Domino based joinery when it's done property and used appropriately. That's no different than any other possible method.

To your point about your table project, 14mm Dominos are my go-to method for a whole bunch of things like that. It's the reason I bought the tool, quite frankly.

[Jim Dwight]

I recently sold my Jet benchtop hollow chisel mortiser. I had not used it since getting my Domino XL. I've used my domino to do a table and cabinet top glue up, frames for tables and chairs, drawer joints, bed frames, and other stuff.

The only ways I see there are potential strength issues can be summarized as mis-application or execution. If you do not get enough glue into the joint, then you can loose strength. You have two mortises to glue up with the loose tenons. So two opportunities for an error. If you limit yourself to the little pre-made tenons Festool offers, you can also have a smaller joint than is really appropriate too. Multiples kind of solves that. But I think a better solution is to just make multiple plunges with the mortiser and a longer loose tenon. Then there is no size difference versus a conventional mortise and tenon. If you make them the right size and glue them up properly, there is no way they are not every bit as strong as a conventional mortise and tenon. You can make mortises wider than 14mm the same way.

But a domino won't make every mortise and tenon joint for me. The curved top rail on my 10 dining room chairs, for instance. Due to the curve a domino mortise would have penetrated the surface of the top rail. So a conventional tenon was cut on the wood before the curve was cut. I happened to use a plunge router to make those mortises because I already had the jig but I could have made the mortises with my domino. All the other chair joints were domino made loose mortise and tenons.

I believe a domino is the fastest and easiest way to make most mortise and tenon joints. I am confident they are just as strong as any other mortise and tenon joint.

[Mark W Pugh]

I recently sold my Jet benchtop hollow chisel mortiser. I had not used it since getting my Domino XL. I've used my domino to do a table and cabinet top glue up, frames for tables and chairs, drawer joints, bed frames, and other stuff.

The only ways I see there are potential strength issues can be summarized as mis-application or execution. If you do not get enough glue into the joint, then you can loose strength. You have two mortises to glue up with the loose tenons. So two opportunities for an error. If you limit yourself to the little pre-made tenons Festool offers, you can also have a smaller joint than is really appropriate too. Multiples kind of solves that. But I think a better solution is to just make multiple plunges with the mortiser and a longer loose tenon. Then there is no size difference versus a conventional mortise and tenon. If you make them the right size and glue them up properly, there is no way they are not every bit as strong as a conventional mortise and tenon. You can make mortises wider than 14mm the same way.

But a domino won't make every mortise and tenon joint for me. The curved top rail on my 10 dining room chairs, for instance. Due to the curve a domino mortise would have penetrated the surface of the top rail. So a conventional tenon was cut on the wood before the curve was cut. I happened to use a plunge router to make those mortises because I already had the jig but I could have made the mortises with my domino. All the other chair joints were domino made loose mortise and tenons.

I believe a domino is the fastest and easiest way to make most mortise and tenon joints. I am confident they are just as strong as any other mortise and tenon joint.

OK, as a novice, I'm not understanding. One of the comments said that the fit was TOO TIGHT for proper glue application. So, is the dominos too tight, or not? Or, in the big picture, most of us would not have to worry about it, because most things we build need not be structurally sound (i.e. building house strong)?

[Jim Becker]

The OEM Domino tenon stock doesn't have a smooth surface. It's got ridges that allow for glue distribution with an "out" at the corners and that also means it's easy to adjust to slightly looser when needed by simple abrasives or scraping. (An example of the latter is when using the 14mm knock down hardware with wood Domino indexing so they can slip in and slip out when something is disassembled)

[Malcolm McLeod]

... the fit was TOO TIGHT for proper glue application. ...

I have not found this to be the case. During dry fit, the occasional Festool pre-made loose tenon inserts so tightly that I can't extract it by hand*, so I use pliers or pinch with a clamp. But a pass on the tenon w/ a block plane, makes multiple dry fits easier. Or just leave it alone, and at glue up, carefully spread glue, and push it home. Neither case has even made me worry about the joints integrity - long or short term.

*- Perhaps like biscuits, a brief stay in the oven would fix this? But never felt the need.

[Ollie McDottie]

Thank you all for your insightful responses. Much like you all, I too use the domino 700 when appropriate and handcut dovetails or box joints or bridle joints or whatever else the specific project calls for. Obviously it's not a panacea for all joining processes. But damn if it ain't pretty useful a lot of the time. In fact, a couple nifty accessories have made it even more useful. The Senco adapter allows me to use the domino 500 bits. Although I've been warned about torque of the 700 on the smaller bits, so far they've worked great. In particular, I use them for cutting the slots for z-style table top brackets. Works like dream. Also, the domino dock sold by Ramon Valdez is fantastic. He actually has a couple of great accessories that I must admit have all been incredibly impressive in their design and fabrication. He also has some pretty cool tutorials on how you can make your own dominos.

In any case, I thank you all for confirming what I had already come to believe to the be the case insofar as the strength of a domino joint. Have a great day and wonderful holiday weekend.

[Derek Cohen]

I have a DF500. It is an impressive tool and a good size for most medium-sized furniture. I purchased it about 5 years ago to build a kitchen with Shaker-style doors and panelling in Curly Hard Maple, and it did a decent job for work which has a limited lifespan. It saved a great deal of effort that my alternative method would have required: traditional mortice and tenon joinery. I did not feel that the joinery would have been as good as traditional M&T (I can induce a tiny bit of flex in the domino joints).



The Domino was not used often after this, but it does get pulled out for jigs or quick builds. This reflects my feeling about this machine. It does the job of joining wood, but this type of joinery has three issues for me ...

1. The Domino joinery (aka loose tenon joinery) is not designed for work which may need to be repaired in the future, and therefore is not used on higher end furniture which is expected to be passed down through generations. Furniture made with dominos are more likely designed to have a short life span.

2. Dominos are a compromise joint. One chooses the size of mortice and tenon closest to that desired. For example, the 1/3 Rule will be abandoned as the width of the domino used may be too narrow. For example, a 6mm domino should be the size for a 18mm thick style. However the domino may lack the width of a traditional mortice and tenon. One solution is to use more than one domino alongside one another. However this may not be possible (insufficient space), and the next solution is to increase the size of the domino to 8mm or even 10mm. This increases stiffness to the joint, but potentially weakens the side reinforcement of the mortice. A true mortice and tenon joint can be made with the optimal design for optimal strength.

3. Domino joinery is easy. Many beginners jump right in and produce some decent looking joinery. The issue for me is that the ease of doing this appears to distract the newbie from a need to understand why certain joinery is the way it is, and there is a flow on effect where furniture is made with little consideration for important factors, such as wood expansion. Does this mean that everyone should earn the right to use a Domino by first learning traditional joinery? I can imagine that some would feel this way.

Regards from Perth

Derek

[Frank Pratt]

Some good, thoughtful ideas presented there, Derek

[Kevin Jenness]

1. The Domino joinery (aka loose tenon joinery) is not designed for repair work, and therefore is not used on higher end furniture which is expected to be passed down through generations. Furniture made with dominos are more likely designed to have a short life span.

Darned if I can see the sense in that statement, unless you are talking about unglued, pinned tenons as used in timber frame joinery. If a tenon glued into a mortise can be removed, reglued and reassembled, so can a spline tenon glued into two mortises. Moreover, a spline tenon glued into a long grain rail is far less likely to loosen up over time due to cross grain seasonal movement. I don't design furniture to have a short life span ,and I use dominos where I think appropriate.

2. Dominos are a compromise joint. One chooses the size of mortice and tenon closest to that desired.

Dominos have as wide a variety of thicknesses as standard tenon joinery, up to 14mm. For wider tenons at any thickness one can plunge overlapping mortises to make the desired width and mill custom splines to fit.

3. Domino joinery is easy.

This is a drawback?

I am all for using the right joint for the job and understanding how to decide that, but I really can't agree with these objections. No offense meant to you, Derek, you are clearly a master of traditional joinery.

[glenn bradley]

The thread is certainly a good presentation of the wide range of varied opinions.