Mafell DDF40 Duo Doweller - Domino now has some competition

[Johnny Barr]

Watched some videos including this one ( https://www.youtube.com/watch?v=Td8aKnDm5cI ) ( https://produkte.mafell.de/en/drilling/duodoweler/duodoweler-ddf-40 ) and I was very impressed and it has sparked my curiosity. The fence is better with a rack and pinion system, a better engineered cross stop, some useful extra stops and 2 quick depth settings. There is also a long and accurate alignment jig for cabinet work. The cutters are 32mm apart which takes care of your shelf systems without the need for an extra jig like Festool's LR32. The other benefit is it uses inexpensive and cheap dowels compared to expensive dominos (unless you making them your self) . It doesn't have the wiggle room setting like the domino but it doesn't need it. Don't get me wrong, I own the Domino and love it and would never give it up, its just this is an impressive and at last a viable alternative. The main problem is there aren't that many Mafell retailers except in Europe/UK and there aren't that many 3rd party suppliers like there are with Festool including Seneca, TSO, FC tools etc. there is a distinct lack of resources
Anyone own one and would care to comment on its pluses and minuses.

[Keegan Shields]

For load bearing joinery, the Domino has superior strength as a true loose tenon. Dowels have very poor strength but are cheap and fast. Every cheap chair I’ve had fail has failed at a dowel joint.

The Domino, Duo Dowler, and biscuit joiner can all do alignment, but only one has the strength of a loose tenon. That’s my thinking anyway. That might not be important to everyone.

[Edward Weber]

For load bearing joinery, the Domino has superior strength as a true loose tenon. Dowels have very poor strength but are cheap and fast. Every cheap chair I’ve had fail has failed at a dowel joint.

The Domino, Duo Dowler, and biscuit joiner can all do alignment, but only one has the strength of a loose tenon. That’s my thinking anyway. That might not be important to everyone.

Dowels and biscuits are simply variations of a loose tenons or a tenon of a different shape. As far as strength goes, a domino is a domino, whereas a dowel can be made of any species of wood or metal. Also a dual dowel can often be used as an aesthetic accent on some projects.
I just don't think it's a good idea to so quickly dismiss something. There are many places this tool could be invaluable.

[Bernie Kopfer]

A dowel is a loose tenon by another name. Does anybody have prices on the new Mafell?

[William Chain]

Looks like its around $1400 here (https://www.timberwolftools.com/mafell-dd40p-duo-dowel-system). Kit comes with a case, three sets of bits, and some other doodads. Priced about the same as the Domino XL, right? Potayto Potahto.

[glenn bradley]

Triton, Grizzly, Freud and others have made "dual dowelers" for some time. They get the same arguments dowels do and get the same support from dowel fans. Despite independent joint tests (the wood failed more than the connector chosen) the back and forth carries on. You know who wins the tests performed by the maker of one or the other; coffee growers say coffee is good for you, wine makers say the same ;). Pick your favorite for your own reasons and carry on ;-)

[Jared Sankovich]

As far as strength goes, a domino is a domino, whereas a dowel can be made of any species of wood or metal.

You could say the same of any loose tenon or domino.

[andrew whicker]

Looks cool to me. I do like the loose domino setting and the ability to make your own tenons for breadboards with the Festool. It would be nice to have both Festool and this. I think this method would require a lot more precision. I like the dominos because I can also be quick with it and if things don't align exactly like it's supposed to I can shave a bit of the domino.

This is a cool idea with cabinetry, especially the shelf height holes. Those height holes never came off to me as high end, so I'm not sure what market is using a hand tool to accomplish them.... Not my world, what do I know.

Per the joint strength argument... the question is how much strength you need not how strong the different types are in comparison to each other. If you have more than enough strength for the required joint then you are done. You've accomplished what is necessary.

[Edward Weber]

You're correct, I was specifically answering the poster who claimed "the Domino has superior strength". I assumed he was talking about the basic domino itself which is a manufactured product, pressed with glue pockets and made out of beech.

A loose tenon joint can take many forms and if used properly the shape of the tenon, round, square or oval, is irrelevant for the most part. Just as how it's cut is irrelevant.

As for strength, it's a ridiculous argument. What type of strength?
When you use a loose M&T, you use what's necessary for the project. A domino is no "stronger" than any other loose M&T used properly in the correct application.

[Keegan Shields]

Soooo not all "loose tenons" are created equal actually. Dowels are weak because they have very little side grain to side grain contact. Compare that to a Domino or similarly shaped loose tenon. Lots of side grain contact. The shape matters a lot.

However, dowels are a cheap and an easy way to automate joinery, which is why they are used in cheap furniture that has a short service life.

Here's a good Rob Cosman video that explains why dowels are terrible for load bearing joints (hint: its because circular holes have almost no side grain in them!) https://www.youtube.com/watch?v=LOI7RVqPNCw

"When you use a loose M&T, you use what's necessary for the project." I couldn't agree more, that's why my comment started with "For load bearing joinery".

Not everyone does what I do, so a duo doweler, or fixed doweling machine, or biscuit joiner or pocket hole might make more sense.

But the fact remains, a Domino shaped loose tenon is stronger than a dowel of similar size.

[Steve Rozmiarek]

Soooo not all "loose tenons" are created equal actually. Dowels are weak because they have very little side grain to side grain contact. Compare that to a Domino or similarly shaped loose tenon. Lots of side grain contact. The shape matters a lot.

However, dowels are a cheap and an easy way to automate joinery, which is why they are used in cheap furniture that has a short service life.

Here's a good Rob Cosman video that explains why dowels are terrible for load bearing joints (hint: its because circular holes have almost no side grain in them!) https://www.youtube.com/watch?v=LOI7RVqPNCw

"When you use a loose M&T, you use what's necessary for the project." I couldn't agree more, that's why my comment started with "For load bearing joinery".

Not everyone does what I do, so a duo doweler, or fixed doweling machine, or biscuit joiner or pocket hole might make more sense.

But the fact remains, a Domino shaped loose tenon is stronger than a dowel of similar size.


Dowels and dominos are all side grain, not sure I understand what you are trying to say. An appropriate sized dowel that cannot be subjected to twisting force, is just as strong as any other loose tenon. In fact a dowel made of the same wood as a domino would actually have higher shear strength than a domino if you chose size based on equal surface areas. Dowels fail when they are used in construction that allows them to twist. Neither loose tenon system has as as much shear strength as a normally sized real tenon with square corners. The shear strength is just a function of cross sectional area.

That being said, any of these can be used effectively within their limitations.

[Andrew Hughes]

I’ve reclaimed wood that was put together with dowels.
Very grateful they used dowels because it came apart so easily. I also learned a thing or two about joints that were poorly prepared and glued.
I vote the domino and the tool to be superior.

[Malcolm McLeod]

Dowels and dominos are all side grain, ....

While the tenon/domino/dowel itself may be 'all side grain' (assuming its made in conventional manner), I believe Mr. Shields may be referring to the end grain portion of the mortice or hole - assuming again, that the mortice/hole is cut perpendicular to the grain in the particular component, i.e. a leg, cut to accept an apron attachment.

Good joint design factors in ALL the loads. A good craftsman should probably have some experience with how their available fasteners/methods will resist those loads.

[Keegan Shields]

Steve,

I agree that the loose tenons themselves are all long grain. But think about the mortises they fit into. A circular hole drilled into the side of a board really only has two little points of side grain for the dowel to be glued to on each side.

Compare that to a Domino/Slot Mortiser/Pantorouter/Handheld Router shaped mortise. The straight sides of the mortise are all side grain for the loose tenon to glue to. See my terrible illustration below of the mortises.

461927

To make matters worse, the commercial dowels I've used have ridges that reduce the side grain contact even further.

Again, not saying dowels are bad or useless. But for serious load bearing joints, the domino shaped loose tenons are significantly stronger (ie. rail to leg attachment on chairs) based on available long grain to long grain glue surface. IMO, that's the capability the Domino offers over its handheld competitors (duo dowler and biscuit joiner). If you don't need that because you only need to align face frames, a biscuit joiner is a cheaper option.

I'm actually moving away from using my Domino since I bought a Maka swing chisel mortiser. I seem to get a much more repeatable result with a stationary tool (less opportunity for user error on my part). Setup takes longer though, that's the tradeoff.

[Keegan Shields]

While the tenon/domino/dowel itself may be 'all side grain' (assuming its made in conventional manner), I believe Mr. Shields may be referring to the end grain portion of the mortice or hole - assuming again, that the mortice/hole is cut perpendicular to the grain in the particular component, i.e. a leg, cut to accept an apron attachment.

Good joint design factors in ALL the loads. A good craftsman should probably have some experience with how their available fasteners/methods will resist those loads.

Exactly, you beat me to it.

[Mike Henderson]

Keegan is correct about loose tenons being stronger than dowels. Like him, I've repaired a lot of chairs and almost every one that had a failed joint (and it's almost always the joint where the seat attaches to the back) it was a joint of two dowels.

Let's look at the mathematics. The numbers used are as follows:

Length of the dowels and the loose tenon = 3"
Diameter of the dowels = 3/8"
Number of dowels = 2
Space between dowels = 1/8"

The two dowels and the space between them will occupy a space 7/8" wide. We'll make the loose tenon fit into that same space. So the loose tenon will be 7/8" wide by 3 inches long.

I'm going to compute the long-grain-to-long grain glue surface for both the dowels and the loose tenon.

The area of a dowel is 2*pi*r*h, where r is the radius and h is the length of the dowel. I'm going to compute the long grain surface area in each side of the joint so h will be 1.5 inches.

The area of the two dowels is 3.534292 square inches in each side of the joint. However, only half of the surface area is long-grain-to-long-grain surface area. The other half is long-grain-to-end-grain. You can visualize this by considering the dowels to be square with the same surface area. Only half will be long-grain-to-long-grain.

The resulting long-grain-to-long-grain surface area is 1.767146 square inches. This is for one side of the joint.

The loose tenon long-grain-to-long-grain surface area can be computed as follows. The loose tenon will be 1.5 inches into the wood and 7/8" wide, giving 1.3125 square inches. Since there are two sides to the loose tenon, the total area is 2.625 square inches. This is for one side of the joint.

The loose tenon has 48.5% more long-grain-to-long-grain surface area than the two dowels.

Additional comments: Most of the wood we work with and most chair parts are about 3/4" thick. It's difficult to put bigger dowels into 3/4" material without compromising the strength. And in the world of commercial chairs, they use 3/8" dowels.
The space between the dowels has been reduced to the minimum in this example. In real chairs, the space between the dowels is much larger. Increasing the space between the dowels allows for a wider loose tenon which provides more surface area to the tenon. The example given here is about as good as it gets for the dowels.

I have a spreadsheet that computes this stuff so if you want me to run other numbers, let me know.

Mike

[Malcolm McLeod]

... Every cheap chair I’ve had fail has failed at a dowel joint. ...


... I've repaired a lot of chairs and almost every one that had a failed joint (and it's almost always the joint where the seat attaches to the back) it was a joint of two dowels. ...

I think we've leaned back in chairs ever since they were first built, so I wonder sometimes if ^this^ is just manufacturers being cheap, or if perhaps 135lb offshore chair designers just haven't caught up with American's passionate love affair with our spoons? ;) (Thus endeth my drift off topic.)

[Jim Dwight]

One reason I make my own tenons is I like them to be wider when that fits the project. That gives me even more side grain contact area in the joint. It is easy to make longer mortises by making multiple side by side plunges. While you could put in more dowels, and maybe offset them so they are not so far apart but you still have the issue of limited side grain on the dowels.

I've never liked dowel joints much. So that bias may influence my belief that the domino makes a better joint. But I agree it is nice Festool is getting some competition. It's a shame the domino costs what it costs.

[Mike Henderson]

One reason I make my own tenons is I like them to be wider when that fits the project. That gives me even more side grain contact area in the joint. It is easy to make longer mortises by making multiple side by side plunges. While you could put in more dowels, and maybe offset them so they are not so far apart but you still have the issue of limited side grain on the dowels.

I've never liked dowel joints much. So that bias may influence my belief that the domino makes a better joint. But I agree it is nice Festool is getting some competition. It's a shame the domino costs what it costs.

When I need wider tenons with my Domino, I just make the mortise wider (with multiple plunges) and then cut one domino tenon so that it, with one full size domino, fits into the mortise. I don't even try to glue the two together.

Mike

[Mike Henderson]

I think we've leaned back in chairs ever since they were first built, so I wonder sometimes if ^this^ is just manufacturers being cheap, or if perhaps 135lb offshore chair designers just haven't caught up with American's passionate love affair with our spoons? ;) (Thus endeth my drift off topic.)

Not at all. US made chairs - made in the 20th century - use two 3/8" dowels. Two dowels will hold the chair together for a while, but if the chairs are used a reasonable amount, the rear joint will fail. It's just a cheaper method of manufacture than using a mortise and tenon and that's why they do it. By the time the joint fails, the chair is out of warrantee and someone like Keegan or me gets it.

If the people want a cheap repair, I drill out the dowel holes and put in slightly larger dowels*. If they're willing to spend a bit more, I'll put in a loose tenon.

Mike

*When the dowels fail they tend to fail on one side of the joint. The other side is still glued so that part of the dowel has to be drilled out. That almost always makes a bigger hole so you have to put in a bit larger dowel. I sometimes turn a dowel to size. Chairs have corner blocks and by the time I get the chair, all that's holding it together are the corner blocks.

[Mike Henderson]

And, by the way, when a dowel joint fails on a chair, it's not the glue that fails - it's the wood. When you separate the joint, you'll see wood attached to the dowel. What happens is that the stress on the joint exceeds the shear strength of the wood and the wood fails. The glue is actually stronger than the wood. So the failed dowel mortise is always larger than the original size because some wood has been pulled out around the hole. That's another reason you have to put bigger dowels in for a repair, if you're going to repair with dowels.

Many people think the hole gets bigger because of movement of the dowel in the hole after the failure of the joint. That may be partially true, but the big reason is the failure of the wood around the hole. After failure, the hole is no longer round so that's yet another reason you have to go bigger - you need to drill out the hole to get it round so the dowel and the wood make good contact.

And, of course, the reason for exceeding the shear strength of the wood is that there's just not enough long-grain-to-long-grain glue surface. Maybe if they would put more than two dowels in that joint it might last longer. Anything to increase the long-grain-to-long-grain surface area.

Mike

[Mel Fulks]

I agree completely with Mike on this one. Some of 3/8” dowels probably failed just because the grain was not straight. I’m betting the
dowel factories don’t check dowel orientation, but….strangely they probably have an orientation for new employees !

[Keegan Shields]

I’m curious where you guys see the Duo Doweler fitting in. We’ve debated the domino, but there are nice stationary industrial doweling machines that are more suited for high volume economy priced furniture than a hand held doweler. What is the Mafel for? Those times when the workpiece is to big to get on a doweling machine?

It seems like the Domino units are far more prevalent than the Duo Doweler. Are they more common in Europe where Mafel has more market share and wider distribution? Is the target cabinet shops?

[johnny means]

For load bearing joinery, the Domino has superior strength as a true loose tenon. Dowels have very poor strength but are cheap and fast. Every cheap chair I’ve had fail has failed at a dowel joint.

The Domino, Duo Dowler, and biscuit joiner can all do alignment, but only one has the strength of a loose tenon. That’s my thinking anyway. That might not be important to everyone.

Your cheap chairs failed because they were cheap chairs, not because of dowels. Dowel construction has proven itself for eons and is still practiced today in fine furniture and construction. That said, I think dowels come with the inherent drawback of not allowing for any error. I think the Mafelle machine falls short in that it doesn't really improve upon a drill and a doweling jig in any real way.

[Keegan Shields]

Again, my point was that the Domino provides a stronger joint than a similarly sized dowel joint. Just because a dowel joint has been used for a long time doesn’t make it stronger than the slot mortise type loose tenon. Perhaps dowels have been used for a long time because it’s pretty easy to drill a circular hole? Design decisions are also made with other factors than quality in mind, (cost? speed?) even fine furniture.

Like all joinery, dowel joints have their place. However, evidence suggests that dowels are, for instance, a poor choice for attaching rails to rear chair legs if you want them to last.

I appreciate that Mike went through the math. I would add that his scenario is probably on the generous side when it comes to the amount of side grain contact in a 3/8” hole, and the dowel still looses.

As further proof, in most of the failed dowel joinery I’ve repaired, the dowel was still firmly glued into the rail (almost 100% side grain contact) but failed in the leg.

[Johnny Barr]

I see it as just an alternative but a very good one. I own a Domino but the Mafell has got me really interested. It has features that are an improvement over the Domino. It has a sliding scale for 2 independent depth adjustments not just preset lengths. It has a very solid rack and pinion fence with a better locking mechanism. The extension (cross stop) is a lot more solid, better engineered, more versatile and locks in to the unit more precisely. The dowel cutters are not limited to 6mm to 8mm but 3mm to 12mm. That 3mm dowel would suit me for the small boxes I make. The included extra stops means you're not limited just by the pins/paddles like on the Domino (37mm/20mm with base support) so needing to reference off pencil lines is at an absolute minimum if at all. Also and obviously dowels are cheap and readily available but I know some make their own loose tenons. Put simply, it is a precision engineered machine with a lot going for it from a very reputable brand. Now for the disadvantages. Its still expensive, it doesn't have the wiggle room setting, (you could drill a bigger hole eg 8.1mm instead of 8mm), there's a lack of resources eg videos, documentation, accessories and as said above its more prevalent in Europe/UK. In Australia, there is only one Mafell authorized supplier and they don't stock anything but order on consignment. Its that lack of a local presence that has stopped me buying it. I can practically get any Festool product same day, I can even take a small drive to a Festool service center but with Mafell its constantly waiting a few weeks for any delivery. I'm really impressed with the Mafell and would even sell my Domino if I had better local support. This is entirely a personal thing.

I think the strength argument is a non argument. Some joints work better with tenons eg chairs and some work just as well with dowels eg joining boards. Some tests I've seen have shown 4 or 5 dowels work just as well as a couple tenons depending on the type of joint. So its not a matter of one or the other, it depends on what you're making, your budget and whether you're a professional, serious hobbyist or a weekend warrior. Dowels suit me and the way I work just as much as Dominos, once again a personal thing.

[Dave Sabo]

I wouldn't be buying/using either if I were making chairs.

If I were making cabinets, the Duo would be the easy choice.

FWIW - I own a domino.

[Johnny Barr]

Y I think dowels come with the inherent drawback of not allowing for any error. I think the Mafelle machine falls short in that it doesn't really improve upon a drill and a doweling jig in any real way.
,
I've used all the dowel jigs from the Dowelmax and Jessem down to the cheapies and their major problem is speed and precision. You think how quickly you can do a mortise with the Domino. The Mafell is just as quick and it even does two holes at once but when you've got a lot to do a doweling jig becomes very slow. Also when doing edge to face joints like with drawers the whole jig has to be rearranged and readjusted and once again this is slow. Doweling jigs even the better ones can't compare with the speed and consistent accuracy of butting up against a pin/paddle like you do with the domino and duo. As for no error I don't see that as a drawback at all with a precision machine. 99% of my mortises with the domino are with the tight setting. I remember Peter Parfitt saying he never uses the wide setting.

[Steve Rozmiarek]

Keegan and Mike, note this part of my post "An appropriate sized dowel that cannot be subjected to twisting force, is just as strong as any other loose tenon. In fact a dowel made of the same wood as a domino would actually have higher shear strength than a domino if you chose size based on equal surface areas."

That's the key, do the math. A dowel of equal surface area as a domino will have more cross sectional area then a somewhat oval shaped domino. A bigger cross sectional area equals more shear strength, as I said all other things being equal.

Mike, you're doing the math wrong. The correlation of the space it takes to fit the dowels and empty space between as to equaling a domino that occupies the same total area is the wrong way to look at it. Like I said, use surface area. To take you analysis to the absurd, why not use 1/8" dowels in the theoretical situation? It'd still justify using the same enormous domino following your logic.

Dominos are fine, so are dowels. Fixed tenons are better. That is the art of good craftsmanship, knowing when and how much.



Keegan is correct about loose tenons being stronger than dowels. Like him, I've repaired a lot of chairs and almost every one that had a failed joint (and it's almost always the joint where the seat attaches to the back) it was a joint of two dowels.

Let's look at the mathematics. The numbers used are as follows:

Length of the dowels and the loose tenon = 3"
Diameter of the dowels = 3/8"
Number of dowels = 2
Space between dowels = 1/8"

The two dowels and the space between them will occupy a space 7/8" wide. We'll make the loose tenon fit into that same space. So the loose tenon will be 7/8" wide by 3 inches long.

I'm going to compute the long-grain-to-long grain glue surface for both the dowels and the loose tenon.

The area of a dowel is 2*pi*r*h, where r is the radius and h is the length of the dowel. I'm going to compute the long grain surface area in each side of the joint so h will be 1.5 inches.

The area of the two dowels is 3.534292 square inches in each side of the joint. However, only half of the surface area is long-grain-to-long-grain surface area. The other half is long-grain-to-end-grain. You can visualize this by considering the dowels to be square with the same surface area. Only half will be long-grain-to-long-grain.

The resulting long-grain-to-long-grain surface area is 1.767146 square inches. This is for one side of the joint.

The loose tenon long-grain-to-long-grain surface area can be computed as follows. The loose tenon will be 1.5 inches into the wood and 7/8" wide, giving 1.3125 square inches. Since there are two sides to the loose tenon, the total area is 2.625 square inches. This is for one side of the joint.

The loose tenon has 48.5% more long-grain-to-long-grain surface area than the two dowels.

Additional comments: Most of the wood we work with and most chair parts are about 3/4" thick. It's difficult to put bigger dowels into 3/4" material without compromising the strength. And in the world of commercial chairs, they use 3/8" dowels.
The space between the dowels has been reduced to the minimum in this example. In real chairs, the space between the dowels is much larger. Increasing the space between the dowels allows for a wider loose tenon which provides more surface area to the tenon. The example given here is about as good as it gets for the dowels.

I have a spreadsheet that computes this stuff so if you want me to run other numbers, let me know.

Mike

[johnny means]

I doubt chairs made in a factory somewhere in Asia would fair any better if the were made with Dominos. If your describing failures in which the glue surface was the point of failure, you're describing a failure of workmanship and not a failure of dowels. All the glue surface in the world is useless if all you do is squeeze in a drop of glue and bang in your dowel/tenon. Also, just measuring the glue surface doesn't tell nearly the entire story. Two dowels spaced apart will often provide more resistance to twisting or racking forces than a single tenon placed in the middle of a joint. Then, of course, there is the problem of comparing those cheesy pine dowels to beech dominos.

[Mike Henderson]

Keegan and Mike, note this part of my post "An appropriate sized dowel that cannot be subjected to twisting force, is just as strong as any other loose tenon. In fact a dowel made of the same wood as a domino would actually have higher shear strength than a domino if you chose size based on equal surface areas."

That's the key, do the math. A dowel of equal surface area as a domino will have more cross sectional area then a somewhat oval shaped domino. A bigger cross sectional area equals more shear strength, as I said all other things being equal.

Mike, you're doing the math wrong. The correlation of the space it takes to fit the dowels and empty space between as to equaling a domino that occupies the same total area is the wrong way to look at it. Like I said, use surface area. To take your analysis to the absurd, why not use 1/8" dowels in the theoretical situation? It'd still justify using the same enormous domino following your logic.

Dominos are fine, so are dowels. Fixed tenons are better. That is the art of good craftsmanship, knowing when and how much.

The analysis that I did was for the real world situation. I didn't use 1/8" dowels because chair manufacturers use 3/8" dowels. And if you want to use dowels that would have approximately the same long-grain-to-long-grain surface area as the loose tenons that I calculated, you'd have to use about 9/16" dowels. The problem with using dowels that large is that it would take up a lot of a 3/4" thick piece of wood. 3/4 (or 12/16) minus 9/16 gives 3/16. That has to be divided in two because you're going to center the dowel. That leaves 3/32" on each side of the dowel which is pretty weak.

No, dowels are not as strong as a good mortise and tenon joint, even if it's a loose tenon. No matter how you look at it - from the mathematics or from experience with failed chair joints - it always comes out with the same answer.

Mike

[And, of course, my analysis is all about surface area.]

[One more thing: A dowel with the same surface area as a tenon does not have greater shear strength. It may have greater torsion (twisting) strength.]

[Mike Henderson]

I doubt chairs made in a factory somewhere in Asia would fair any better if the were made with Dominos. If your describing failures in which the glue surface was the point of failure, you're describing a failure of workmanship and not a failure of dowels. All the glue surface in the world is useless if all you do is squeeze in a drop of glue and bang in your dowel/tenon. Also, just measuring the glue surface doesn't tell nearly the entire story. Two dowels spaced apart will often provide more resistance to twisting or racking forces than a single tenon placed in the middle of a joint. Then, of course, there is the problem of comparing those cheesy pine dowels to beech dominos.

The failures we see in chair joints are not glue failures. The dowels are well glued. The problem is that the wood that the dowel is glued to fails in shear.

Mike

[Greg Quenneville]

I think Mafell had the patent on those locating pins. The first generation domino had those, but Festool was forced (so the story goes) to come up with a different solution, hence the little tabs on the later domino 500. I have the XL which again uses locating pins. Mafell enjoys a great reputation in Europe, so the quality is there. Dowels? Nothing says “IKEA” quite as well.

[Mike Henderson]

One interesting question is why do the chair manufacturers only put two dowels in that joint at the back of the chair seat. It's clear that two dowels do not provide sufficient long-grain-to-long-grain glue surface area to stand up to normal use for many years. An additional dowel might provide enough additional glue surface area to provide a much longer life for that joint.

My belief is that there's no value to them in adding that additional dowel. Two dowels will allow the joint to survive for perhaps five or more years and by that time the customer probably forgot where they purchased the chairs. People seem to just accept these joint failures on chairs.

Mike

[Rich Engelhardt]

3/8" dowels were fine in chairs until people began to swell up to pachydermatic proportions (like me!).
Now a fat-boy-tubby-gut like me can wreck a chair PDQ just be sitting on it...

[Jared Sankovich]

This popped up in my IG feed this morning. You could ask his thoughts on the mafell vs the others.
461936

[Charlie Jones]

Most all the joint failures I have seen over the years involved dowels. There are places they make sense but not many. I don’t think the Domino has any competition from Mafell. Loose tenon and tenon joinery is just better. Especially since the Domino became available. That said, the Domino could use better adjustments. They could learn from my Dewalt biscuit joiner which has a rack and pinion fence and marks on the side to indicate the center of the cutter. I really like the machine but it is not perfect.

[andrew whicker]

If I put my engineering hat on (which I haven't for a while) then here's my take.

A broken dowel is the result of a failure, but is not the failure. The failure in these cheap chairs (in my experience) is when the leg and the rail are no longer one solid piece. Whatever happens after that is a result of that failure. That's where we have to look.

So, the question then is what causes a chair to get wobbly (i.e. the rail and the leg to come apart) and I can see only one culprit: the glue didn't hold the two pieces together under stress. BUT, we have to dig deeper because that can driven down into more large categories:
1. The glue failed because it wasn't strong enough
2. The surface area the glue needed wasn't enough
3. The design of the chair didn't distribute the torque correctly, etc.
4. The glue wasn't applied properly

I don't immediately blame the dowel just because it broke. A domino may have survived, but you would have still been given a chair to fix. Also, to be clear, unless someone is jumping on the seat of these chairs and pin is broken directly in the middle of the joint, these are not failing in shear. My guess is they are failing in tensile or bending. But again, by the time the pin finally gives out, it's been trying to take on the a lot more work than it was designed to do. If you're interested, you can look up pieces of wood materials failing in different scenarios and then look at the pins you get that are broken and compare to verify how the pin broke.

Example:
We once had a client that had terrible fatigue cracking problems in their shafts (compressors). So the shafts would eventually vibrate as the crack propagated deeper and deeper. The failure wasn't the crack, the failure was the corrosion on the outside of the shaft that created high stress zones that allowed the crack to start. Once the crack started, the shaft already failed. So we had to fix the corrosion (shaft material, customer changes their process, etc).

[lowell holmes]

See this site for reasonable cost.

https://images.search.yahoo.com/search/images;_ylt=AwrJ61UgHABhrVAA_IpXNyoA;_ylu=Y29sbwNi ZjEEcG9zAzEEdnRpZANDMjAwM18xBHNlYwNwaXZz?p=dowl-it+1000+self-centering+doweling+jig&fr2=piv-web&type=E211US739G0&fr=mcafee

https://www.homedepot.com/s/dowel%2520jig?NCNI-5

[Mike Henderson]

If I put my engineering hat on (which I haven't for a while) then here's my take.

A broken dowel is the result of a failure, but is not the failure. The failure in these cheap chairs (in my experience) is when the leg and the rail are no longer one solid piece. Whatever happens after that is a result of that failure. That's where we have to look.

So, the question then is what causes a chair to get wobbly (i.e. the rail and the leg to come apart) and I can see only one culprit: the glue didn't hold the two pieces together under stress. BUT, we have to dig deeper because that can driven down into more large categories:
1. The glue failed because it wasn't strong enough
2. The surface area the glue needed wasn't enough
3. The design of the chair didn't distribute the torque correctly, etc.
4. The glue wasn't applied properly

I don't immediately blame the dowel just because it broke. A domino may have survived, but you would have still been given a chair to fix. Also, to be clear, unless someone is jumping on the seat of these chairs and pin is broken directly in the middle of the joint, these are not failing in shear. My guess is they are failing in tensile or bending. But again, by the time the pin finally gives out, it's been trying to take on the a lot more work than it was designed to do. If you're interested, you can look up pieces of wood materials failing in different scenarios and then look at the pins you get that are broken and compare to verify how the pin broke.

Example:
We once had a client that had terrible fatigue cracking problems in their shafts (compressors). So the shafts would eventually vibrate as the crack propagated deeper and deeper. The failure wasn't the crack, the failure was the corrosion on the outside of the shaft that created high stress zones that allowed the crack to start. Once the crack started, the shaft already failed. So we had to fix the corrosion (shaft material, customer changes their process, etc).

The failures we see in chair joints are not broken dowels. The dowel pulls out of the mortise in the back of the chair. The failure is not a glue failure - there is wood still attached to the dowel. The failure is that the stress on the dowel (outward) exceeds the shear strength of the wood that the dowel is inserted into. The remaining hole, after taking the joint apart is larger than the original hole, another indication that it was not a glue failure.

Glue is stronger than wood and we see that in the failure mechanism of a rear chair joint.

The solution to this problem is to increase the long-grain-to-long-grain glue surface area. A tenon has more surface area than two dowels. Perhaps 3 dowels would provide better holding power.

Mike

[Brian Holcombe]

I think they fail because they are not designed to include enough splay, the joinery is often installed perpendicular for ease of manufacture, the structure isn’t well supported and the joinery is not well chosen or sized.

The bridge didn’t fall over because of the tack welds, it fell over because there was only tack welds...

[andrew whicker]

I misread the shear. I thought you meant the pin sheared.

I wonder how many other problems you are fixing at one time... better glue, tighter / smarter clamping, bigger tenon, better wood for tenon, etc.


The failures we see in chair joints are not broken dowels. The dowel pulls out of the mortise in the back of the chair. The failure is not a glue failure - there is wood still attached to the dowel. The failure is that the stress on the dowel (outward) exceeds the shear strength of the wood that the dowel is inserted into. The remaining hole, after taking the joint apart is larger than the original hole, another indication that it was not a glue failure.

Glue is stronger than wood and we see that in the failure mechanism of a rear chair joint.

The solution to this problem is to increase the long-grain-to-long-grain glue surface area. A tenon has more surface area than two dowels. Perhaps 3 dowels would provide better holding power.

Mike

[Edwin Santos]

I doubt chairs made in a factory somewhere in Asia would fair any better if the were made with Dominos. If your describing failures in which the glue surface was the point of failure, you're describing a failure of workmanship and not a failure of dowels. All the glue surface in the world is useless if all you do is squeeze in a drop of glue and bang in your dowel/tenon. Also, just measuring the glue surface doesn't tell nearly the entire story. Two dowels spaced apart will often provide more resistance to twisting or racking forces than a single tenon placed in the middle of a joint. Then, of course, there is the problem of comparing those cheesy pine dowels to beech dominos.

This has been my experience as well. When I make a dowel joint, I am doing so with care and taking the time to paint the dowel completely with glue,and use a long swab to paint the inside of the hole completely with glue. The failed factory chairs I have encountered have looked like a machine was squirting glue into the hole before the dowel was inserted with the expectation that the glue would wick its way up the flutes or spirals. Some of them were made with "pre-glued" dowels which are a case study in compromises.

The most recent chair repair I did was a failed mortise and tenon joint. That's right. What happened was the customer's teenage daughter was leaning back in the chair while sitting at the dining table doing her homework. So the chair seat levered against the rear legs and the failure was in the surrounding wood above the joint that was insufficient to stand up to the torque so it gave way to the load.

This points to the larger issue.
It is not reasonable to declare one type of joinery superior to another in a vacuum or based on a singular criteria like surface area calculations. Every furniture design is unique in terms of the load situation. It is tempting to think bigger is always better but like the recent repair I did, (that particular) M&T joint simply removed too much native wood.
There are times when a well made and properly sized mortise and tenon is the best choice, and there are times when a well made dowel joint is a better choice. It's up to the craftsman to consider the pros and cons of different joinery approaches and make a rational selection.

For anyone interested enough in this subject, here is a link to a detailed test done by Mattias Wandel on the two types of joints being discussed here: https://woodgears.ca/joint_strength/dowel.html

I think his conclusion supports what I am saying above, which is that neither type of joinery is "better" than the other. It really depends on the situation, design and execution of the joint.

[Johnny Barr]

Great post Edwin and hopefully this might get people back on the main topic of comparing the duo dowler and the domino

[Andrew Hughes]

Edwin had me on board until he mentions Mattias Wandel the YouTuber.
The dominos makes a mortise with round corners. It. Doesn’t take much effort to square them up with a chisel and cut a integral tenon on the other half.
A mortise that’s square to the face of work piece isn’t as appreciated as it should be. Floating or integral it’s very strong.

[Eric Arnsdorff]

461993
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I only included the Jess Em doweller but there are others. My bias (because I own one and dang it is made well) may be why I only included the Jess Em Dowel Jig. I'm very impressed with the precision and usability of the Jess Em dowel jig. But clearly not as fast as the Festool Domino. I also really like my biscuit jointer.

My personal preference is the dowels because of the wider range of applications. As mentioned before they can also be a decorative element along with an alignment tool in addition to providing a strong joint.
Since woodworking is my hobby I struggle with buying the Festool domino. But it definitely appears to be a good tool and a versatile joining method for someone wanting to make some money with their time in the shop I can see some advantages. It's also hard to beat my biscuit jointer for the applications it is good for.

I'm surprised at Mafell's offering. I like dowels but at that cost I don't see the Mafell advantage. It appears much less versatile than my Jess Em doweling jig and doesn't appear to offer any significant advantage over the Festool Domino. Maybe I'm missing something but the marketing I looked up sure doesn't point it out.

I noticed most of this thread got into what the beliefs are for joint design and strength. When I read these it makes me think how glad I am that structural building codes as well as material science, strength of materials and mechanics of deformable bodies do not rely on this belief system. I know that may strike some wrong but there is a lot of science behind what strength is along with how to predict such failures with tons of empirical data backing the science. I've seen case studies with nothing controlled and comparison of much smaller dowels compared to larger mortise and tenon joints with a conclusion that mortise and tenon is "stronger". The fact is a dowel can be made many times stronger than a much smaller tenon. Additionally, if stronger is the only thing that matters then steel of the same dimensions will be stronger and tungsten will be stronger than that, etc...

However, even though I really like dowels for my workshop, I would buy the Festool Domino well ahead of the Mafell Doweller.

[Sean Nagle]

One interesting question is why do the chair manufacturers only put two dowels in that joint at the back of the chair seat. It's clear that two dowels do not provide sufficient long-grain-to-long-grain glue surface area to stand up to normal use for many years. An additional dowel might provide enough additional glue surface area to provide a much longer life for that joint.

As a fan of Windsor style chairs, joining a seat to a back is just bad design ;)

[Brian Holcombe]

Most of the Danish designs I’ve admired set them back legs at such a splay that they are difficult to rock. This helps prevent people from rocking them.

The industry, however, tests chairs by rocking them to failure. One can learn a lot by doing this, I’ve done so to my own design.

[Jim Becker]

Most of the Danish designs I’ve admired set them back legs at such a splay that they are difficult to rock. This helps prevent people from rocking them.

The industry, however, tests chairs by rocking them to failure. One can learn a lot by doing this, I’ve done so to my own design.

Yea, I've noticed those small incremental changes you've made to the angles. Chairmaking is an engineering art-form!

[Edward Weber]

Well said Eric

[Brian Holcombe]

Thanks, Jim!

[Jonathan Jung]

Every try cutting a door apart, right through the dowels at the joints? The ones I've seen are shrunk away from the edges of the hole. Dowels have their purpose, but for me, it's only alignment, not long-term strength. Rob Cosman is right.

[Eric Arnsdorff]

Every try cutting a door apart, right through the dowels at the joints? The ones I've seen are shrunk away from the edges of the hole. Dowels have their purpose, but for me, it's only alignment, not long-term strength. Rob Cosman is right.

I understand that seeing something like this could cause you to decide to choose a different method in your builds.
However, if a dowel shrunk away from the surrounding material how would any other joinery technique of the same materials not do the same?

[Edward Weber]

The Domino is a good tool and makes the task of cutting a mortise quick and easy. Just because you have a Domino doesn't mean you don't have to understand proper joinery techniques. Many times this just makes cutting mortises in the wrong place or wrong size quicker. The same thing can be said for the Dual Dowel machines. You still need to have an understanding of joinery.
Also just because doweling machines cut 2 holes in one operation doesn't mean that that's equivalent to one domino.
The Domino has only been around for less than 15 years. In the grand scheme of things, they're not even a blip. For every chair made with dominos, there probably about one million or more made with dowels.
All the little anecdotal stories everyone has about chairs or doors or whatever failing because of dowels, is statistically inconsequential. While I'm sure all your stories are true, they are such a minuscule percentage of all the dowels used thus far that haven't failed, it's not really even worth trying to compare.
Dowels have a several thousand year head start on dominos and a track record to rely on.
The way some of you portray dowel joints, it's as if everything made before the year 2000 is just junk and all the dowels will eventually fail?

[Charlie Jones]

The Domino is a good tool and makes the task of cutting a mortise quick and easy. Just because you have a Domino doesn't mean you don't have to understand proper joinery techniques. Many times this just makes cutting mortises in the wrong place or wrong size quicker. The same thing can be said for the Dual Dowel machines. You still need to have an understanding of joinery.
Also just because doweling machines cut 2 holes in one operation doesn't mean that that's equivalent to one domino.
The Domino has only been around for less than 15 years. In the grand scheme of things, they're not even a blip. For every chair made with dominos, there probably about one million or more made with dowels.
All the little anecdotal stories everyone has about chairs or doors or whatever failing because of dowels, is statistically inconsequential. While I'm sure all your stories are true, they are such a minuscule percentage of all the dowels used thus far that haven't failed, it's not really even worth trying to compare.
Dowels have a several thousand year head start on dominos and a track record to rely on.
The way some of you portray dowel joints, it's as if everything made before the year 2000 is just junk and all the dowels will eventually fail?

Dowels were used because it was a convenient way to get the job done. That is especially true for commercial furniture. If they had easier and faster methods they would have used them. The Domino is simply the dowel of our time. It is fast, easy and it works. I have used biscuits for years. They work but are not as versatile as the Domino. That being said dowels are still the best for some situations.

[Steve Rozmiarek]

The Domino is a good tool and makes the task of cutting a mortise quick and easy. Just because you have a Domino doesn't mean you don't have to understand proper joinery techniques. Many times this just makes cutting mortises in the wrong place or wrong size quicker. The same thing can be said for the Dual Dowel machines. You still need to have an understanding of joinery.
Also just because doweling machines cut 2 holes in one operation doesn't mean that that's equivalent to one domino.
The Domino has only been around for less than 15 years. In the grand scheme of things, they're not even a blip. For every chair made with dominos, there probably about one million or more made with dowels.
All the little anecdotal stories everyone has about chairs or doors or whatever failing because of dowels, is statistically inconsequential. While I'm sure all your stories are true, they are such a minuscule percentage of all the dowels used thus far that haven't failed, it's not really even worth trying to compare.
Dowels have a several thousand year head start on dominos and a track record to rely on.
The way some of you portray dowel joints, it's as if everything made before the year 2000 is just junk and all the dowels will eventually fail?

YES!!!! Add that there is a whole relatively new category to throw away furniture that is designed to a price point. This stuff is made to be fashionable and cheap, then get tossed. Of course it's sort of attractive but horrible stuff, it was never designed to be anything but. It's useful though for a specific purpose, it was not meant to be used for many years. Of coure the joinery is junk in it, most customers wouldn't pay for anything better. We've all had some, and as woodworkers we can surely recognize that this type of furniture is not to be compared to the real stuff.

[Edward Weber]

I don't disagree but just because the Domino may be to some "the dowel of our time", it doesn't make the existing dowels any less effective.
To me the joints effectiveness depends on the craftsman's knowledge more than the style of loose tenon being used. Just because you use dowels in your joinery, it does not automatically mean your joints will be weaker than if you used a Domino. Size, placement, orientation, number, species, etc., all come into play.

[Dave Sabo]

lso just because doweling machines cut 2 holes in one operation doesn't mean that that's equivalent to one domino.

In some respects it's better. Can't drill 32mm system holes for cabinetry with a domino at all.

Dowels are still used for cabinet carcass construction all over Europe ( an a few in the USA) but I'm not aware of any factory using a domino or similar sized tenon at all. Dowels are more than adequate when used within their design envelope. Same as a domino.

Like Edward said - you have to know when and where to use a particular technique for the best outcome. A domino won't make you any better a craftsman or designer than you already are.