what’s wrong with Domino joinery

[Ollie McDottie]

Hello Everybody.

I apologize if this is a repeated thread or query, I did do a search to see if it’s been addressed elsewhere and didn’t find apt answers.

I’m a big fan of my domino. I use it as much as I can and it has never failed me. Joining boards for table tops, rails, stiles, aprons, legs. If I can get the machine in there, I’ll use it.

However, I’ve heard more than once that it’s not structurally sound. That really it’s more of an alignment tool than a joining one, like a biscuit joiner. And frankly I’m totally confused by this. How is a tightly/well fitted loose tenon glued on both sides not performing a structural capacity? What am I missing here?

Say for example, I’m making a table base with an apron — How is a fat 14mm domino glued a good inch or more into both sides of the joint not as strong as a tenon cut out of the apron going into a mortise cut out of the leg or a sliding dovetail/bridle joint/etc.?

As always, great gratitude for all of the fantastic insights you all share so generously here. And if I’ve missed the thread that addresses this, please redirect me.

[Stewart Lang]

Nothing's wrong with it. Some people just *think* there's something wrong with it :)

[Keegan Shields]

Like everything in woodworking, I think there are tons of ways to accomplish most tasks.

I like to have options when it comes to joinery, but its important to understand the strengths and weaknesses for each method in a given application.

I like my Domino, but I also use a router, a swing chisel mortiser, dowels, dovetails, splines, half laps, box joints, mechanical fasteners, tongue and grooves and so on....

As a general rule, if all things are equal, the joinery method with more long grain to long grain glue surface is stronger.

You also have to consider the type of force you think will be applied to a joint. M&T joints are really strong in shear but much weaker when being pulled apart.

For pulling forces (tension I think?) a wedged through mortise and tenon joint is much stronger. Or you can add dowels to pin M&T joint.

And then there are all of the cool joints that aren't in common practice...

So many fun things to learn in woodworking!

-Keegan

[Brian Holcombe]

I’d rather just size out and cut something closer to ideal with free standing machinery. Nothing ‘wrong’ with domino joints other than that. They can be accurate or sloppy depending on the user and the prep.

[Andrew Hughes]

I did some testing with domino loose tenons. The results very good !

[Richard Coers]

Make a few samples and then destroy them. I picked up some cutoffs from a friends shop that had been joined with dominoes. There was no wood transferred between the domino and the walnut mating piece. That has me concerned and I want to do some samples myself. Personally I think the dominos are too tight and makes for a slightly dry joint, or the striations on the domino make for a thick glue line. But I want to see wood fibers on both sides when the joint fails.

[Patrick Kane]

I think some of those critiques leveled against the DF500 are fair. It can only plunge 25-28mm, which isnt tremendously deep. I also think 10mm is pretty weak for most furniture joinery. Thats my opinion, i do think there are structural concerns with the DF500's joinery in typical furniture joinery. However, i have the 700 now, and i cant level much critique towards its joinery capacity. It can plunge almost 3" of depth, and 14mm has some substance in numbers. Ive used it on king size bed frames, a 13' dining room table, and a bunch of chairs and smaller end tables. On really big projects, i think the 700 is slightly outgunned. For example, on the 13-14' dining room table the long aprons are connected into the legs via a very hefty dovetail. I used the 14mm dominos for the short apron connection to the legs. I didnt feel comfortable with the 14mm dominos being strong enough for that 9' span, and the majority of the stresses in that table are on the long apron joint.

Its a fantastic tool and suitable for 80% of joinery needs, but i dont think its a panacea. I also think half the fun of woodworking is exposed joinery, or complex joinery. That is how i use the domino. If it wont be seen, and its up to the task then i use it every time. If it can be seen, or the domino is undersized for the potential forces at play, then i do it "by hand". And by hand, i mean a table saw/shaper for the tenon, and a router and chisels for the mortise.

[Matt Day]

Ignore those people. It’s simply a floating tenon. Very good strength when used and sized appropriately.

[Alan Schwabacher]

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.

[Mike Henderson]

The Domino has worked very well for me in a lot of situations. No complaints or problems.

Mike

[Albert Lee]

its floating joinery... been around for a long time... long before the Domino were invented.
for domino made by the 500, yes, its probably not strong enough as its only 25-28mm deep. but the 700 is different story. I have 700, 500, and Mafell Zeta P2. different horse for different course.

[Jeff Roltgen]

I've built and sold close to 100 bar stools, all joinery done with a DF500 and 10mm dominos. None have been reported as coming apart over ~6 year span of production.
This includes a couple in the shop that get abused regularly.
I will continue to build this way with confidence.

[Mike Cutler]

Ignore those people. It’s simply a floating tenon. Very good strength when used and sized appropriately.

Bingo!!!

I don't own a Domino, I don't need one. I can cut M&T's all day long, a dozen other ways, cheaper. Blah, blah, blah.
If someone ever gave me one though, you better believe I'd use the beejeezus out of it !!!
Most folks, myself included, have a problem with the initial investment in the tool, and try to argue it away. It doesn't detract one iota from the actual value of the tool though.
They're nice. They really are. Keep using it within it's capabilities and you'll be fine.
Sometimes I wish I didn't know a dozen other ways to cut M&T's. ;)

[Eric Arnsdorff]

The biggest problem with it is I don't own one!

I've had other tools I wanted/needed (ok wanted) more and can make do without one just like everyone did before the tool was available.

Strength statements are so very often subjective and I rarely see proper testing that would hold up to any scientific rigor. I used some dowels in a skinny face frame recently. A domino would have been "stronger". But so would a carbon fiber face frame, etc. But I don't need stronger for something that already has a safety factor in the triple digits. I also wouldn't use a wood domino to join a structural steel weldment. As stated here many times - it's about the application and not what is "stronger".

So if you'd like to fix my problem with Dominos ... I'll PM you my address for shipment ;-).

[glenn bradley]

It is just a speedier way to do a lot of sizes of floating tenon joinery. When my requirement is too large or too small or otherwise not suitable for the Domino I use mortise chisels, a router or whatever I used to use for everything before I got a Domino. I have never used the factory domino biscuits but, assume they are as good as the ones I make myself out of whatever stock I am using for the piece. I think a couple of the responses got it right; what's wrong is that you don't have one or that you want to convince yourself that something is wrong with them. I don't see the benefit of a radial arm saw. That doesn't mean that there's anything wrong with them. A gazillion RAS lovers can't be wrong :)

[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).

https://i.postimg.cc/CKDQKHBz/F1.jpg

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.

[Warren Lake]

the joinery derek uses has done the test of time and old guys I knew kept using it even when time saving gizmos were around. Likely they would look at a piece and not feel as good about it as had they not built as they were taught.

[Jim Dwight]

The biggest issue I have with Derek's views is he assume we all use only Festool pre-made tenons. The only Festool tenons I've used came with my XL (I bought it used) and were 12mm thick. They seemed to fit fine to me. They were fairly tight but the indentations should hold a little glue. I think the indentations would tend to help you get enough glue into the joint.

What I have almost always done is to make my own tenon stock. It is super easy and fast and I just use up scrap so there is no cost. In addition, I can make them wider and, if necessary, thicker than stock tenons. The machine will make repeated plunges with part of the bit in the previous hole. It still cuts smooth and easy. Normally I am just making a longer mortise. I think the widest I've made was about 6 inches long (in a crib, Wood magazine design). If you make your own tenon stock you can make them fit however you want.

There isn't anything wrong with beech for tenons - I am pretty sure that is what Festool uses - but I prefer to have tenons of the same wood as the rest of the project.

A domino machine just cuts a mortise. If you don't like the idea of a loose tenon just make an integral one. No way it needs to be inferior in any way to any other mortise and tenon joint.

I also use a Seneca adapter to use smaller bits in my XL. I think any argument against this is just thinly disguised marketing for Festool. No issues for me.

[Tony Zona]

Ollie,

I don’t have a domino machine, but they seem like a good idea.At the Cleveland, Ohio, museum I ran across this.464148And they showed the inside of another.464149Check it out. Loose-tenon joinery has stood the test of time. You can see it right here. Use it if you have it with no apologies. The ancient Egyptians would have, if they had one.

Cick on the pictures to enlarge them.

[Warren Lake]

if you are trying to make a point for festering you should show us joinery in a rail and style, not a spline to align two case pieces. They didnt use a mortise and tennon as its side grain to side grain.

Egyptians used mortise and tennon and germans likely before them.

[Charlie Jones]

Good point. Those mortises are rounded. Perhaps they had a Domino or a router jig!

[Derek Cohen]

The biggest issue I have with Derek's views is he assume we all use only Festool pre-made tenons. The only Festool tenons I've used came with my XL (I bought it used) and were 12mm thick. They seemed to fit fine to me. They were fairly tight but the indentations should hold a little glue. I think the indentations would tend to help you get enough glue into the joint.

...


Jim, I could equally argue that many may not own an XL, nor does the average punter make their own custom dominos. The most common Domino machine is likely to be the DF500 (such as mine), and my comments are directed at those that use the commercial dominos.

Nevertheless, I am not meaning to appear argumentative, nor suggesting that using the Domino makes one second rate woodworker. As is often mentioned, we should not blame our tools. However, when I look around the various woodworking fori, what I so frequently see are pieces of work poorly conceptualised. My analytic side identifies this as a product of taking shortcuts. A Domino is not responsible for this - in the right hands it is a wonderful tool - but its strength also may deliver a weakness.

I am interested in using my DF500 more often. As you helpfully point out, it is a tool for making mortices. It is up to us to understand this and then to explore how it may be developed past the basic machine-sized dimension.

The issue of repair-ready joinery is partially a feature of the way we use a domino. How many here use hide glue? Hide glue is reversible and repairable (it accepts glue-on-glue). It is more likely, but not a given, that someone using a domino will be seeking to work quickly (since this is its strength) and using a PVC glue. PVC glue is not glue-on-glue and does not come apart easily for a repair. Of course, there is no assurance that a more traditional joint will be glued any differently.

My purpose for making these points was to raise awareness of the issues, some obvious and some hidden.

Regards from Perth

Derek

[Jim Dwight]

Derek (and others),

I agree completely that the ~1 inch deep mortises the DF500 makes are not deep enough for many projects. That is a bigger limitation, in my mind, than the 10 mm cutter. I can make a wider mortise than 10mm with multiple passes but I can't "fix" a 1 inch deep mortise. This limitation was the biggest reason I went with the DF700. 2 3/4 inches has been enough at least so far. No regrets.

For those who have not used one, the mortises the domino makes are very, very similar to those made by a plunge router. Smoother walls than I got from my hollow chisel mortiser.

I also agree with Derek that the big advantage of the domino is speed. But I would add speed with precision. It is easy to get a good mortise where you want it quickly with a domino. I use more mortise and tenon joints because I can do them so quickly and well.

I am no festool fan. The domino is the only festool power tool I own. It does something than no other tool can do so quickly and well. But it is also extremely possible to make mortises many other ways.

Jim

[Bryan Cramer]

I’ll throw my opinion in as well. This has been a very good discussion and some good points have been made. I have a DF500 and honestly use it more for cabinetry and even solid wood carcasses. It’s just as fast a a biscuit joiner but makes a stronger joint. It’s great for traditional face frames as well. I still think it’s comparable to glued mortise and tenon joinery however if you draw-bore the joint it far exceedes only glue for strength and longevity. Therefore I’ll be sticking with traditional joinery for critical joints table leg to apron, doors, etc. A well executed drawbored joint closes up without clamps once the pin(s) are driven home.

[Mike Henderson]

I was using my Domino today with the 4mm dominoes. It really is a nice tool - very accurate and easy to use.

Seems that I wind up using it on just about every project I do.

Mike

[Stan Calow]

I appreciate Derek's reminder that strength is not the only important criteria in joinery.

[Prashun Patel]

I think our tastes and aesthetic preferences has less longevity than a Domino joint in many applications.

About the only places I wouldn't personally use an appropriately sized domino joint is on a chair or something similar that gets stressed and wracked and twisted and loaded often.

I have and will use them on tables of any size.

[Mike Henderson]

The thing to remember is that the Domino is not a binary tool. That is, use the Domino in those places where its strengths come into play and use other joinery where the Domino is not the best solution.

I use the Domino on just about every project I do and I appreciate its speed and accuracy. But for certain joints, as Prashun points out, I'd use some other technique.

Mike

[Jeff Roltgen]

Surprised so much resistance to use on chairs. Look at it this way - what else are you going to fit into a 1.5 -1.5" leg with 2.5 -3" seat stretchers connected from 2 different directions? How about a 1x1.5" stretcher with a single 10mm domino on each end? Please, enlighten me and tell me the proper method of joinery. (mortise and tenon, right? but we've established that's what a domino is, except for one word: "loose".)

While I understand size matters for mortise and tenon work, there is barely enough real estate to fit four 10mm dominos at that leg joint. In some instances, you still need to miter the ends of the dominos just to pack it all in there. And of course, corner blocks are used under the seat at each corner to brace inside of joint as well.

Now, consider the joinery of mass-produced factory chairs. You'll be sold a "chair", but in fact, receive a chair kit that you get to assemble, likely including some glue-up, right there on your own dining room floor. Please explain how a domino is such a travesty to use in place of that methodology?

Methinks those that challenge it's use for a chair have likely never actually built a chair.
Make a sample of your own, and I think you'll find it's quite robust.

[Prashun Patel]

YMMV, but I've built a fair number of chairs, and even one with dominos. I've also bought and assembled enough cheap chairs to make these conclusions:

A lot of commercial chairs - even expensive ones - will wrack and wobble and come apart after several years of reasonable use. I wouldn't use that as a bench mark for dominos. The bar should be higher.

The Maloofs I've made use screws and (critically) dados that resist those forces better. The Windsor chairs and stools I've made use joints under compression and tapered sockets and the users weight to lock joints. These work well.

The chair I made with dominos was a poor aesthetic design. So I dismantled it before I completed it. I was shocked how easily the 10mm dominos dislodged. I dropped the chair deliberately and then sat on it and really rocked back and forth just to see how easily the joints would fail. They started to wobble easily. A quick rap with a rubber mallet caused the joints to come out easily. This wasn't a scientific experiment, but i believe that that dominos don't hold all that well when shocked like this. In fact, glue in general doesn't hold well when smacked or shocked. That I know. A chair can be vulnerable to this kind of force in normal use if it tips over or gets dropped.

In my experience, a chair benefits from mechanical strength in the form of integral tenons, shoulders, and even screws.

YMMV, but I'm comfortable with my experience on this. You can make your own conclusion.

[Jim Dwight]

Some would call this diversity of opinion but I think it is more nonsense. A domino just makes a mortise. Period. It makes good, smooth sided precisely dimensioned mortises. There is nothing about a domino mortise that is inferior to a mortise made any other way. If you want a tenon thicker than 14mm, plunge multiple times. If you need one deeper than 2 3/4 inches I will have to give you that one but how many projects need mortises deeper than 2 3/4 inches? If you want a mortise wider than a domino makes with that cutter, just plunge multiple times. I've done them over 6 inches wide (for a plywood tenon, not a solid one).

I have 10 chairs I built this year in my dining room. The only joint in the chair that was not made with my domino is the top back rail. It is curved so a straight loose tenon would have come through the surface. So the tenons need to be integral. I could have still done the mortise with my domino but I already had a jig to use my plunge router so that is what I used. All the stretcher joints were make with my domino and have loose tenons. The tenons are the same size as called for in the plans I got from Woodsmith - or a little bigger. The tenons are cherry, the same as almost all the rest of the chair. I have curved spindles in the back that are also joined to the chair with domino mortises although these pieces are not glued (as called for in the plans which assumed traditional mortise and tenon joints). Most but not all the mortises required more than one plunge of the tool to make - they are wider than one plunge of a domino makes. No big deal. Very simple to do.

I sit on my chairs. I have no problem with anybody sitting on these chairs. I am not real heavy, 185, but my son and son in law are both 200+. These chairs do not care. I have similar chairs with ladder backs made before I was aware of a domino that have been used for several decades and work fine. I am very sure the most recent chairs made with domino made mortises will also last decades.

If you have failed domino joints they were either incorrectly sized for the connection or you did not glue them properly. Made and assembled correctly domino joints are no better or worse than other mortise and tenon joints. Because they are just another way to cut these joints. This is repetitive for me to say but I think it is important to emphasize that the fact that dominos only come in certain sizes is not a reason to use smaller mortise and tenon joints and hope for the best. Just spend a very few moments and make some larger loose tenons. Or make a wider mortise and an integral tenon.

Blaming a machine you did not use correctly for a weak joint you made is not going to get you better projects. Learning from your mistakes and doing it right the next time is how you will make progress. Several decades ago when I started I messed up pretty throughly at times. Most but all the projects were salvagable. I still make mistakes. But I don't blame my tools for my mistakes. I try to learn from them and I make fewer than I used to.

It also occurs to me, however that what I think domino joinery is may be different than others are thinking. I am thinking of mortise and tenon joints with at least the mortise cut with the domino tool. If you add in the use of the Festool pre-made tenons, you add opportunities for issues. Like smaller tenons than you really need, either in width or length (primarily due to the 25mm maximum cut depth of the 500). I wonder if the pre-made tenons may sometimes swell up if stored for a long time in a humid environment and limit the glue in the joint making the joint weaker. I don't think how we make the mortise makes the joint weaker and therefore lesser but if the use of this tool causes us to use smaller joints than the project really requires - then that would definitely be a problem. If using swelled up tenons that starve the joint for glue that could be a problem. But I do not see the mortising tool as an issue - especially the 700 model I use. It will cut deep enough tenon length should seldom if ever be an issue.

[Prashun Patel]

You may be right, Jim. I may have made them wrong. I own that. If people read my post as anything more than one person's opinion then let me disabuse them of that. It's just my personal conclusion. I'm no pro.

But right or wrong, if feasible, I do trust an integral tenon on chairs more than a Domino. It's because I trust the integral side a little more than if both sides were floating.

I hope the reader sees my post as nothing more than a personal, prejudiced opinion.

[Jim Dwight]

Prashun,

Thanks for your reply. I think I said this in a previous post but I do think that having two mortises to apply glue to is an additional source of error in a floating tenon joint that an integral does not have. But the floating tenon joint does not have the shoulder cutting source of potential error. Tight fitting shoulders help resist loading in chairs. So I do not see the risks of my mistakes as higher with the floating tenons. But I have no problem at all with somebody going the other way. It's nice we have choices.

But if I wanted to use integral tenons I would still make the mortises with my domino. I just do not see a reason to spend more time doing them any other way.

Jim

[Jeff Roltgen]

Jim and Prashun,
One more interjection that may help clarify the angle I'm seeing this at. I am in agreement to provide chairs/bar stools of the most economical yet strong variety to a local upholstery shop for them to ultimately add some upholstery to, then sell the complete units to their clients, = no time for integrated tenons and Maloof-style joinery. This is why I sing so highly the praises of the Domino. An erosion of pride I guess, given I'm more of a traditionalist, but hey - gotta make a living, and the occasional calls for a batch here and there is a welcome addition to round out the schedule each year. These chairs are considered heavy duty in every way, yet priced to actually be marketable. Heck of a tall order, pinched between Vietnamese imports and heirloom grade, bespoke furnishings.
Really would like to dissect one of the $1200-$1400 Amish chairs to see if they're using dowels, mortise and integrated tenon, or (gasp) dominos...? wouldn't be terribly surprised. :p
Anyhow- it's been an interesting, good spirited debate!

Jeff

[Carl Crout]

I found this on a Festool group:

Here's the link if it's allowed: https://festoolownersgroup.com/index.php?pretty;board=festool-tools-accessories;topic=domino-joint-strength.0

Fine Woodworking published the results of joint strength tests in their January 2009 issue (#203). They tested eighteen joints: half laps, bridle, mortise and tenon, floating tenon, miter, splined miters, dowel max, bead lock, domino, biscuits etc. They attached a rail to a stile with various joints and tested them in a lab under controlled conditions for lever strength. The range of the results ran from 1660 pounds of breaking strength for the half lap joints to a meager 200 pounds for the stub tenon. Traditional mortise and tenon rated near the top with a breaking strength of 1444 pounds followed very closely by floating tenon at 1396 pounds The bad news is that the domino placed #14 out of 18 at a lowly 597 pounds, just above biscuits at 545 pounds.
I replicated these tests for half lap, mortise and tenon, floating tenon, biscuit, and of course domino. I used used 1x2 1/2" stock and a simple vise and my arm. I performed the tests twice for each joint, once in red oak and once in white pine. I used Tightbond's original glue and allowed each joint to dry for three days. Obviously I can't give a psi specification for breaking strengths, but I can tell you that my results paralleled those published. The half lap was incredibly strong , The mortise and tenon and floating tenon were also very very strong. The biscuit sheared off easily, but this was no surprise. Sadly the domino (#8 50 floating) joint broke with sickening ease. The domino (#8 50 tight) joint was a bit tougher, but was not very impressive. Using two dominos if you can work them in substantially improved the joint, but fell well short of a mortise and tenon or floating tenon. The shortcomings of the domino surprised and saddened me. The questions for Festool Domino owners is why so weak and what do?
In my opinion, the weakness results from the relatively slim glue surface of the domino. This shortcoming has in my opinion been exacerbated by
the impressed pattern on the Festool dominos. Initially, I assumed that the beech domino was meant to swell like a biscuit and the impressed pattern on the domino would swell up and disappear. But this was not the case. On the joints I tested these impressed patterns did not swell out from immersion in water based glue, but remained impressed. I do not know what Festool hoped to achieve by adding these impressions, But they result in a further reduction of glue surface. They reduce the wood to wood contact by creating a series of gaps along the whole glue surface thus weakening the joint.
So what to do? The answer is simple; increase the glue surface by widening the glue surface and getting rid of the impressions. You do this by using the domino joiner to make traditional floating tenon joints and making up wide smooth floating tenons. I recently made up red oak floating tenons 1 3/4" wide x 2" long for the #6 domino bit. Making up yards and yards of tenon stock is simplicity itself with a band saw and a planer. I cut matching mortises in rails and stiles by lining up 2 Domino machine cuts to make a 2" mortise including the corners which provides a 1 3/4" flat surface. I then glued up the joints using the smooth, wide, oak tenons. The resulting joints are enormously strong: far, far stronger than using the dominos. This method was quick and easy and produced true chair-strength joints. So the Domino machine is a great addition to my shop, but without the dominos!

[Carl Crout]

Then there is this: dowelmax vs domino

https://www.youtube.com/watch?v=_vgAeGCATgM

[Jim Dwight]

Carl,

I've seen that test in FWW. It proves that if you compare a bigger mortise and tenon joint to a smaller one, the smaller one will be weaker. Not sure it proves anything else. It looks like you agree.

I have not purchased a Festool tenon or a Festool cutter for my Domino. I use CMT or Amana cutters. I ruined the 12mm Festool cutter mine came with and had to get an Amana replacement. I see no difference. Except the price is half as much. I make my own tenons for the reason you cite - I can make them the right size for my project - and also because I am cheap and I don't like wasting time. I normally can make all the tenons I need in less time than it takes me to go to the store and buy some. If I am hard pressed for time I may buy some someday but only if the size is right for what I am trying to do.

It seems like we agree even if we don't say things exactly the same. Use the domino to make the mortises you need easily and quickly. Then make tenons to match (or cut integral ones if you prefer).

Jim

[James Jayko]

I’ll throw my opinion in as well. This has been a very good discussion and some good points have been made. I have a DF500 and honestly use it more for cabinetry and even solid wood carcasses. It’s just as fast a a biscuit joiner but makes a stronger joint. It’s great for traditional face frames as well. I still think it’s comparable to glued mortise and tenon joinery however if you draw-bore the joint it far exceedes only glue for strength and longevity. Therefore I’ll be sticking with traditional joinery for critical joints table leg to apron, doors, etc. A well executed drawbored joint closes up without clamps once the pin(s) are driven home.

You can always pin a domino tenon...