Dowel Joinery?

[Andrew More]

So I saw a youtube video (https://www.youtube.com/watch?v=-FFM7TTCWig&t=140s) recently about dowel joinery which reminded me that I've seen almost no discussion of it. It appears to fill a similar niche to the Festool domino, while not requiring a very expensive unitasker. It also appears to be stronger than pocket holes, or biscuits and fill a similar niche.

I just assembled a few simple panel glue ups with it, using this cheap jig (https://www.homedepot.com/p/Milescraft-DowelJigKit-Complete-Doweling-Kit-with-Dowel-Pins-and-Bits-1309/300534138), and it appears to have worked as well as biscuits or dominions for doing alignment, with the advantage that it appears to add strength in a way that biscuits do not. If you don't want to spend the $20 for the jig, there are instructions in this video (https://www.youtube.com/watch?v=-FFM7TTCWig&t=140s) on how to make your own.

Any ideas why dowels don't get much attention, while pocket holes, and more traditional joinery techniques, such as dovetails, and mortise and tenon appear to be all the rage? Is there a serious draw back that makes the domino the superior tool for this? I'm guessing the domino makes a stronger joint, but not sure by how much, and how significant that difference is.

[Edwin Santos]

Dowel Joinery rocks!

I hate to use the term better or worse, all I'm saying is dowel joinery has been a great method to have in my repertoire.

In answer to your question, commercial furniture has contributed to giving dowels a bad name. In a factory setting they are using machinery to squirt a glob of glue in the dowel hole, and then another machine to push in a dowel. The result? A glob of glue at the bottom of the dowel hole and the vast majority of the dowel body dry and unglued. These are the dowel joints that come apart and make people curse dowels.

An attentive woodworker on the other hand is coating the dowel hole (I use cotton swabs like long Q tips) and also coating the dowel itself before inserting and then clamping the joint together. This is a very different scenario than the factory one I describe above.

I happen to have a Jessem Doweling jig which is a superb piece of kit. However for many projects, I end up making a shop made doweling jig for the specific purpose.

Edwin

[Andrew More]

In answer to your question, commercial furniture has contributed to giving dowels a bad name. In a factory setting they are using machinery to squirt a glob of glue in the dowel hole, and then another machine to push in a dowel. The result? A glob of glue at the bottom of the dowel hole and the vast majority of the dowel body dry and unglued. These are the dowel joints that come apart and make people curse dowels.

Good to know, I must admit to falling into that error. I'll avoid it in the future. However I'm also making a panel, so lots of glue along the edge, so I don't think it's going to come apart, but next time I'll be more attentive to glue in the hole as well.


I happen to have a Jessem Doweling jig which is a superb piece of kit. However for many projects, I end up making a shop made doweling jig for the specific purpose.


Thanks for the pointer to the Jessem doweling jig. Seems far superior to the cheap piece of plastic I've been using. Can you post some pics of your hand made jigs? I'm curious as to their construction, and how you ensure high levels of accuracy with them.

[Mike Henderson]

Dowels have their place but they're not as strong as mortise and tenon. I've posted the mathematics several times here.

Mike

[Bruce Wrenn]

Instead of a fancy drill guided jig, use a plunge router with up spiral bit and a shop made guide. Guide is simply a piece of wood with a couple holes drilled to accept guide bushing and a fence

[John TenEyck]

For edge joints you don't need anything for strength and dowels won't add to the strength of a glued edge joint. However, you may choose to use dowels, biscuits, whatever, to help align edge joints. I often use biscuits because they are fast.

My beef with dowels is they are slow compared to other joints, and require very high precision for perfect alignment of the mating parts, and it grows nearly expotentially the more dowels you have in a joint. I've seen folks show 8 dowels in some joint, all perfectly aligned. Great, but how long did it take to make compared to a Domino or loose tenon joint? For most applications other joinery techniques are just easier and faster for me, so the only time I use dowels is where they are about the only option, like some chair joints where you are working with pieces of small cross section.

John

[Mike Henderson]

In answer to your question, commercial furniture has contributed to giving dowels a bad name. In a factory setting they are using machinery to squirt a glob of glue in the dowel hole, and then another machine to push in a dowel. The result? A glob of glue at the bottom of the dowel hole and the vast majority of the dowel body dry and unglued. These are the dowel joints that come apart and make people curse dowels.

Edwin

I'm afraid this is not true. I've repaired a lot of chairs that use two 3/8 inch dowels between the seat and the back. The failure is not from lack of glue. The chair manufacturers are not incompetent and do coat the dowels quite well with glue.

The failure method is not glue failure but wood failure - the wood that the glue is attached to actually breaks.

The problem with dowels on that chair joint is that there simply is not sufficient long-grain-to-long-grain glue surface area. A tenon that will fit into the space of two 3/8 inch dowels has quite a bit more long-grain-to-long-grain surface area and thus provides a stronger glue joint. I'll post the mathematics (again) if you have questions or doubt if this is true.

Mike

[jack duren]

Only failure on dowels is time. Almost anything can fail in time. Old glues, wrong glues,not enough glues, too much moisture... Any number of reasons.

When you build something hut simple care to do the best you can to prevent future problems...

[Mel Fulks]

Ive used them. We would cut them from dowel rod, didn't use the spiral stuff. We would drive them thru a 1 inch thick
piece of scrap steel that had different sized holes. The sharp edges on the steel were beveled off with a countersink.
The plate did no cutting ,only squeezing. We thinned the the glue just a little. The dowels went in easily and swelled
quickly.

[glenn bradley]

As you have probably gotten from the responses; they have their place. Many joinery methods can be interchangeable for a given set of requirements. You can search here and elsewhere for near-endless discussion on the long grain to long grain versus round and flat "objects de' joinery". Some of us have love or hate relationships with certain things like dowels, biscuits or whatever. These feelings are built through experiences. I would argue that many joinery types can be misused and provide sub-optimal performance whether in strength, durability or fussiness ;-)

[Edwin Santos]

I'm afraid this is not true. I've repaired a lot of chairs that use two 3/8 inch dowels between the seat and the back. The failure is not from lack of glue. The chair manufacturers are not incompetent and do coat the dowels quite well with glue.

The failure method is not glue failure but wood failure - the wood that the glue is attached to actually breaks.

The problem with dowels on that chair joint is that there simply is not sufficient long-grain-to-long-grain glue surface area. A tenon that will fit into the space of two 3/8 inch dowels has quite a bit more long-grain-to-long-grain surface area and thus provides a stronger glue joint. I'll post the mathematics (again) if you have questions or doubt if this is true.

Mike

Not true?

Well here's my source (besides my own experience) - an article written by Bob Flexner, a well known published woodworker whose article mentions Brian Boggs, also a well known published woodworker: https://www.popularwoodworking.com/flexner-on-finishing-woodworking-blogs/gluing-dowelled-joints-why-factory-furniture-works-loose-so-quickly/

By the way, I am in no way saying dowels are "better" than a mortise and tenon, or any other kind of joinery for that matter. However I do not agree with sweeping nature of your conclusion regarding one being inferior to the other. While I understand the long grain to long grain surface concept, in reality if the dowel joint is well made and well glued, they are more comparable than your statements would suggest. As a source to further elaborate on what I am saying, here is a link to the tests Matthias Wandel did measuring the strength of the two types of joinery: https://woodgears.ca/joint_strength/dowel.html

I do think a mortise and tenon joint in most circumstances will be stronger, but not radically so. In my own woodworking I tend to use dowels in applications and places where a mortise and tenon would not be possible or practical. In applications that lend themselves to mortise and tenon joinery, I use a mortise and tenon.

Edwin

[Malcolm Schweizer]

These doors were doweled with the JessEm doweling jig I bought from
another creeker. I was skeptical, but really loved it. I also used it to repair some mahogany doors. The repair was doweled for strength.

423715

[Michael A. Tyree]

Yes they have their place no matter what you might read. I keep spirals on hand and also have a store bought dowel plate that grooves them as i cut to length. This allows keeping a general stock of long hardwood dowels at hand for ready use. Lowe's keeps them on the back aisle in several woods- I buy oak ones there on my 10% vet discount.

[Mike Henderson]

Not true?

Well here's my source (besides my own experience) - an article written by Bob Flexner, a well known published woodworker whose article mentions Brian Boggs, also a well known published woodworker: https://www.popularwoodworking.com/flexner-on-finishing-woodworking-blogs/gluing-dowelled-joints-why-factory-furniture-works-loose-so-quickly/

By the way, I am in no way saying dowels are "better" than a mortise and tenon, or any other kind of joinery for that matter. However I do not agree with sweeping nature of your conclusion regarding one being inferior to the other. While I understand the long grain to long grain surface concept, in reality if the dowel joint is well made and well glued, they are more comparable than your statements would suggest. As a source to further elaborate on what I am saying, here is a link to the tests Matthias Wandel did measuring the strength of the two types of joinery: https://woodgears.ca/joint_strength/dowel.html

I do think a mortise and tenon joint in most circumstances will be stronger, but not radically so. In my own woodworking I tend to use dowels in applications and places where a mortise and tenon would not be possible or practical. In applications that lend themselves to mortise and tenon joinery, I use a mortise and tenon.

Edwin

Okay, here's the math.

Let's take dowels that are 3 inches long, 3/8 inches in diameter, and two are used in the rear of a chair joint.

To compare to a tenon, we'll look at the length of the dowel that's in one side. The tenon is solid wood on one side of the joint.

The formula for the surface area of a cylinder is 2*pi*r*h. In this situation, r is 3/16 and h is 1.5 inches so the area of the cylinder is 1.767 sq inches. Since we have two dowels, the total area of the two dowels is 3.534 square inches.

However, only half of that area is long-grain-to-long grain surface area. You can visualize this if you think of the dowel as a square dowel of the above surface area - half will be facing long grain and half will be facing end grain.

So the long-grain-to-long-grain surface area is 1.767 square inches.

Now let's look at a tenon that will fit into the same space. The first question is how far apart are the two dowels. The further apart they are, the wider the tenon can be to fit into the same space. So let's assume the two dowels are close together. On chairs they aren't but let's do it this way to be conservative - let's assume the two dowels are 1/8 inch apart.

So the tenon can be 3/8 + 3/8 + 1/8 inch wide, or 0.875 inches. Since the tenon is going to be 1.5 inches long, the surface area of one face is 1.3125 sq inches. The tenon has two faces so the total long-grain-to-long-grain area is 2.625 square inches. This is 48.5% greater than the long-grain-to-long-grain surface area of two dowels and provides significantly greater strength.

Note that in the real world dowels on chairs are spaced further apart than 1/8 inch so the area of the equivalent tenon is going to be greater, giving a much higher long-grain-to-long-grain surface area.

I have a spread sheet that computes this if anyone would like to play with the figures.

Mike

[All the chairs that I've repaired have had two dowels at that rear joint and the failure was wood failure, not glue failure. I've never had to repair a joint that was M&T. Two dowels just don't have enough glue surface area for that joint.]

[Edwin Santos]

Okay, here's the math.



Mike

[All the chairs that I've repaired have had two dowels at that rear joint and the failure was wood failure, not glue failure. I've never had to repair a joint that was M&T. Dowels just don't have enough glue surface area.]

Thanks for the math. Sounds good in theory.

Do you have a comment on the source articles from Flexner and Wandel?
Wandel's test in particular reveals a real world outcome very different from what your math implies (in theory).

Ironically I repaired a chair about three weeks ago that the customer bought from Restoration Hardware. The mortise and tenon joint failed. There appeared to me to be two problems. One was that the mortise and tenon joint had left so little "meat" on either side of the mortise that it broke right through the back leg. The other looked to be what might have been insufficient glue.

Again, not lobbying for one kind of joinery over another 100% of the time.
One thing people don't always consider with a mortise and tenon joint is the wood that's being removed from one member and whether there is sufficient surrounding wood left to handle whatever load is transferring through the tenon. When I've seen mortise and tenon failures it's been for this reason primarily. I think both types of joinery have their place. The key is to use each one where appropriate.

One other point, I think two dowels, especially if they were not coated completely with glue, may be culprit behind your repairs more than the whole method of joinery being unsound. One thing I like about the Jessem system is the ability to do rows of dowels, in an offset pattern to minimize surrounding wood failure. If the chairs you have been repairing had been joined with a row of three or four dowels and both the hole and dowel were brushed with glue like you or I would do in our shops, I think you would see fewer failures. Again, I'd reference you to Flexner's article who does a better job of explaining it.

Edwin

[Thomas McCurnin]

I haven’t used dowels or biscuits in years, although I still have my 40 year old doweling jig and my Porter Cable biscuit machine. I find that properly jointed edge joints with Titebond works good enough for me. While in theory they help with alignment, I sometimes find the opposite is true—if the hole or biscuit mortise is not 100% accurate, I’ll get lippage which can’t be fixed by crawls and clamps. At least with a naked Titebond joint what you see is what you get.

For chairs, I wouldn’t use anything but a mortise and tenon.

I did have an occasion to repair some cheap 30 year old furniture and found that the dowels had shrunk and failed. I plugged the holes with new wood and epoxy. Then re-drilled the dowel holes, found perfect sized dowel stock (not easy) and epoxied those in place. It’s holding under high weight.

I would not voluntarily use biscuits or dowels unless the design or glue up required it.

[Mike Henderson]

Thanks for the math. Sounds good in theory.

Do you have a comment on the source articles from Flexner and Wandel?
Wandel's test in particular reveals a real world outcome very different from what your math implies (in theory).

Ironically I repaired a chair about three weeks ago that the customer bought from Restoration Hardware. The mortise and tenon joint failed. There appeared to me to be two problems. One was that the mortise and tenon joint had left so little "meat" on either side of the mortise that it broke right through the back leg. The other looked to be what might have been insufficient glue.

Again, not lobbying for one kind of joinery over another 100% of the time.
One thing people don't always consider with a mortise and tenon joint is the wood that's being removed from one member and whether there is sufficient surrounding wood left to handle whatever load is transferring through the tenon. When I've seen mortise and tenon failures it's been for this reason primarily. I think both types of joinery have their place. The key is to use each one where appropriate.

One other point, I think two dowels, especially if they were not coated completely with glue, may be culprit behind your repairs more than the whole method of joinery being unsound. One thing I like about the Jessem system is the ability to do rows of dowels, in an offset pattern to minimize surrounding wood failure. If the chairs you have been repairing had been joined with a row of three or four dowels and both the hole and dowel were brushed with glue like you or I would do in our shops, I think you would see fewer failures. Again, I'd reference you to Flexner's article who does a better job of explaining it.

Edwin

More than theory - I've seen this in practice.

I have not seen ANY chairs in for repairs that showed signs of not having glue on the whole dowel. And I would not expect to see that. The companies who manufacture chairs are not incompetent. As I said several times before, what I've encountered is broken wood, not glue failure. When I've taken the joint apart there is wood still stuck to the glue of the dowel. The failure is wood failure, not glue failure, and the problem is insufficient glue surface.

In my calculations, I've assumed 3/8 inch dowels and tenons that are 3/8 inch thick. I have not experienced any failures where the wood of the chair side or back broke away. The stress on that chair joint is generally levered apart (from people rocking back), and not side-to-side.

My point is that a mortise and tenon that fits into the same space as two (or more) dowels is significantly stronger than the dowels. Those woodworkers who want to create long lasting chairs would be advised to use M&T and not dowels.

Mike

[And regarding chair joint failure - Thank Goodness for corner blocks. Sometimes that's the only thing holding the chair together.]

[Mel Fulks]

I have no doubt that Mike's figures are correct. When it is deemed best to use dowels to replace a broken tenon, the
dowels need to have larger diameter. One cause of failures ,and I mean looseness as well as complete failure, is an ill
fitting of the two meeting surfaces.

[Mike Cutler]

I've repaired a number of antique doors through the years. Just got done with one over 100 years old last year. The dowels are big, 1/2" diameter and about 8" long. They go deep into the rails and stiles of a door,and are usually spaced about 2"-3" apart. I've never repaired a broken dowel, or had them come out easily. They almost always broke/split the wood on the face of the stile.
Dowels are like any other joinery technique. They have their applications. They do require a significant effort to maintain symmetry and uniformity of a joint, or it won't go together. Antique doweling machines, when you can find them, are still very expensive.
They will not equal the strength of a properly sized and fitted M&T joint, but they will be stronger than the two pieces of material they are joining together, if sized properly.

[Mike Henderson]

Another thing that supports the glue surface area problem is that when I repair a chair with two dowels at the back joint, the dowels that are into the seat side are almost always still solidly glued into the side. The side that has come loose is the dowels into the chair back.

The reason is that the dowel into the side of the chair is all long-grain-to-long-grain surface area because the dowel goes into the wood along the grain, not across it. The dowels into the back of the chair go into the side of the wood, across the grain, so half of the dowel is facing end grain. The dowel into the side of the chair has twice the long-grain-to-long-grain surface area compared to the dowels into the back of the chair.

Mike

[Von Bickley]

I'm just a old retired disabled woodworker and cannot justify buying a Domino, so I will continue using my dowel jig. I have used dowels on several projects and have no problems with alignment or strength.423762

[tom lucas]

I've used dowels for years on edge to edge joinery. Good as any other, even if slow to make. I've not had a failure yet. However, I only use them in end-to-face joinery when nothing else would work. I'm with Von on the domino thing. I cannot justify the cost of a domino. I'll use dowels, biscuits, or make mortise & tenon joints. Biscuits are really fast, but not as strong as dowels. So, I mainly use them where there a good number of joints that don't see a lot of stresses. I do get how the domino is useful, and likely worth every penny for professionals where time is money.

[Will Blick]

Mike, interesting take on the dowels gluing to end grain over half their surface area. I am curious if you ever viewed the videos and explanations on the DowelMax site showing how Dowels are stronger than MnT. thoughts?

While I certainly see the inherient strength of a MnT joint, I am curious if you feel the multi dowel joint would have its own set of unique benefts. A MnT joint is a single joint. When the two mating surfaces expand and contract at slightly different rates over time, this runs the risk of the glue bond breaking or weakening the ENTIRE joint. I have witnessed this in old furniture. Specially when u join two different wood species. With dowels, the surface areas is so small for each individual dowel, (compared to the single MnT length) it seems dowels are much less vulnerable to this type of bonding failure.

I would assume in a majority of applications, the breaking force of either MnT or dowels FAR exceeds any real world forces that would be applied to it. So proving one or the other will break at 3k lbs vs. 4k lbs, is a moot point when the joint may only be subjected to 200 lbs max in the real world. Therefore, possibly maintaining the glue bond over time is the more critical factor. would u agree?

On the issue of panel glue ups,
I often like to clamp tight, to assure seamless glue joints. Its so rare to get PERFECTLY straight edges...and even when you do, within a few hours, the wood moves. This is why TiteBond recomends 150 to 250 psi on the joint lines. Its to overcome non straight edges, not for the glue to bond. This is a LOT of force, which is a lot of clamps with 3/4 material.

When I clamp with NO joinery, the boards can slip n slide a bit, its inevitable. I have tried end clamps, massive allum. bars across the glue lines, with there own set of clamps, but the wood can still creep, requiring more work to flatten the surface of boards that started out perfectly flat.

I agree with a previous poster, biscuits are not ideal for this, despite their long standing repuation for this task. Sometimes, biscuits work, other times, they cause more problems than benefits, specially with fast drying glue and inconsistent thickness of the biscuits. Loose tenons are a good option for sure as you only need a snug fit in one direction, so it is relatively fast, on par with biscuits. I have had good luck with the Domino for this task, albeit, you consume a lot of $ in dominos for panel glue ups. Dowels are dirt cheap and fit really snug. And with the dowelmax, its not that difficult to align the holes perfectly on both boards. With a dry fit, you avoid any alignment surprises during glue up. I rather put the time into the glue up, vs. the clean up of the glued panel.

[Gordon Stump]

I use dowels when I have to. Like on the large mitered frame of a gaming table I recently made. Or the arched door of Shaker tall clock I made years ago. Without a biscuit joiner or loose tenon machine, using dowels made sense. Not my first choice but plenty strong. My biggest problem with them is the time it takes to glue up. Recently I used 24 hour T-88 and that solved that.

[Mike Henderson]

Mike, interesting take on the dowels gluing to end grain over half their surface area. I am curious if you ever viewed the videos and explanations on the DowelMax site showing how Dowels are stronger than MnT. thoughts?

DowelMax would hardly be an unbiased source for the comparison of dowels to M&T, now would they?

Dowels have their place and have been used for many years. A dowel joint can be sufficiently strong for a particular application. The key is to make sure you have sufficient long-grain-to-long-grain glue surface area for the particular joint and the stress on that joint.

My comments were specifically about chairs and the way the seat is joined to the back with two 3/8 inch dowels on most commercially made chairs - it's simply not strong enough and the reason is because there's just not enough long-grain-to-long-grain glue surface area. If they put in more dowels, perhaps in a zigzag pattern, they could create a strong enough joint. I suspect they don't do it for cost reasons - and because the dowel joint lasts about as long as most people keep chairs.

But if the chair manufacturers wanted to create a stronger joint, a loose tenon would probably be quicker and easier to manufacture than putting in more dowels.

My advice to anyone making a chair is to use a M&T joint in the back of the seat, instead of two dowels, if they want the chair to last.

Mike

[For lining up boards in a panel glue up, consider the use of cauls. They do a really good job of keeping the boards aligned during a glue up. Another approach (a bit slower) is to do two boards at a time and then add boards one-at-a-time to the first two boards. That allows you to do a better job of keeping the boards aligned.

None of those alignment techniques - dowels, biscuits, Dominos, etc. - add any strength to the joint and they take time to do. Also, you can run into a problem a friend of mine had. He used biscuits and wound up having to trim the panel in such a way that he cut through a biscuit (it showed on the edge).]

[Edwin Santos]

More than theory - I've seen this in practice.

I have not seen ANY chairs in for repairs that showed signs of not having glue on the whole dowel. And I would not expect to see that. The companies who manufacture chairs are not incompetent.

I don't think anyone is saying the companies that manufacture chairs are incompetent. What Bob Flexner (certainly not incompetent) is saying in the article I linked is that manufacturers are working around efficiency constraints that are sometimes defined by their machinery and cost pressure due to market competition. The operating theory they are using is to drill a hole with one machine, and squirt a glob of glue into it with another machine, and insert a fluted dowel with yet another machine. The expectation is that the glue will wick up the fluted dowel, which happens to some degree and is why you are seeing some glue on the whole dowel. However this method is considerably different than the care you or I would take in our own shops where we might use a brush and liberally coat the dowel and the hole with glue.

This is why I liked Matthias Wandel's test because being a one man small shop, I'm sure he was applying glue to all joints just as we would do, not using the factory methods. And of course his outcome was that the strength of a dowel joint and a mortise and tenon joint were surprisingly similar.

Anyway, I am not promoting a dowel vs. mortise and tenon argument, I am a fan of dowels where they are appropriate and I will say I think they are much stronger than you suggest. If they were not, then James Krenov and his legions of Krenov school alumni are missing the mark, as is Brian Boggs who builds his chairs exclusively with dowels. And Sam Maloof used an elaborate joint held together with screws which could only rate poorly using your math as a criteria.

Edwin

[Will Blick]

Mike, after 30+ years in the business world, I am wise enough to realize who is putting out test results and the chance of bias. However, just because a partial party shows a test result, doesn't in itself, make the test a sham. I have NO dog in this fight... as I mentioned, I use everything...the right joinery for the job. I was just curious if you have seen the test, and if you had any comments on it. I was complimentary about your methodical approach towards this issue in my post. I guess, my bad for asking. I will refrain in the future.

I marvel that a few hot topics with ww's, such as dowels vs. dominos, vs. biscuits, or, number of clamps for panel glue ups....
these topics seem to force some people to bunker down in their camps, and defend at all costs. I will never understand this, but such is the world of forums! Not just ww, Ford vs Chevy, Apple v Android, PC v Mac, etc.

[Mike Henderson]

And Sam Maloof used an elaborate joint held together with screws which could only rate poorly using your math as a criteria.

Edwin
I can't possibly see how you got to this from what I posted. Screws are entirely different from dowels and M&T and joints using them can be quite strong.

I have repaired a lot of doweled chairs and I've observed how the dowels failed. As I've said many times before, the failure mode is not glue failure (or missing glue) but wood failure. There is wood stuck to the glue on the dowels which indicates that the dowel has been pulled out of it's hole. And since the glue is stronger than the wood, the wood broke when the dowel was pulled out. And there was glue on the whole dowel - solid dowels, not those with spiral or fluted grooves. It is very clear that the failure is not due to poor assembly or poor glue application.

So I started analyzing why that happened, which led me to realize that there just wasn't enough glued surface area to withstand the tension forces. Then I analyzed the surface areas and realized that only half of the dowel is getting glued to long grain.

What other people do when they build furniture is up to them. For me, it's easy to see that two dowels on the back of a chair seat is not strong enough and that a M&T in place of that will be stronger. The mathematics I provided will tell you how much stronger.

Mike

[Let me go through some analysis.

First, just about everyone has encountered dining room chairs where the back joint has failed. A simple test is to put your knee on the seat that pull and push the back from the top. If the back moves back and forth, the joint is almost always loose.

Second, we see this in dining room chairs of all different designs (but much more often in chairs without stretchers), all different woods, and all different manufacturers.

Third, when we disassemble the chair we usually find that the joint consists of two 3/8 inch dowels, and the dowels are loose in their holes. Most of the time, the loose part is in the back, not in the side.

Removing the dowels, we find that they are different wood species and that they show evidence of glue on the whole surface. They are not fluted or spiral dowels. Further, we find pieces of wood still attached to the glue on the dowels.

What is our theory of the failure?

Your theory is that the glue was not applied properly to the dowels or the holes. Let's examine that. To accept that we'd have to have many manufacturers in many different countries all with the same problem of improperly applying glue to the dowels and dowel holes. Further, we should have reports that the dowels removed from those failed chairs are dry, at least on a significant portion of the dowel. However, I have not heard any such reports and have not seen that myself. Additionally, I believe that chair manufacturers are more competent than that. I can think of several ways of applying glue evenly to the dowels and holes with a machine, and controlling the amount of glue for cost reasons and to avoid glue escaping and being visible after assembly. It's very hard to believe that they would be so crude as to just shoot a wad of glue into the dowel hole. I would rate that theory as unlikely.

Another theory is that the manufacturers do a good job of applying the glue but there is just not sufficient glue area on two dowels, especially on the chair back, and the dowels are being pulled out, breaking the wood that the glue is attached to. In support of that we can calculate the amount of long-grain-to-long-grain glue surface area and compare it to a M&T joint. From observation, most of the time the dowel is pulled out from the chair back, and not the chair side which has more glue surface area. Additionally I have reported that most of the dowels removed from failed joints have wood still stuck to the glue of the dowel.

If you wish to continue with your theory that the chair manufacturers are not glueing the dowels properly, you need to provide some evidence other than hearsay.]

[Edwin Santos]

I can't possibly see how you got to this from what I posted. Screws are entirely different from dowels and M&T and joints using them can be quite strong.

I have repaired a lot of doweled chairs and I've observed how the dowels failed. As I've said many times before, the failure mode is not glue failure (or missing glue) but wood failure. There is wood stuck to the glue on the dowels which indicates that the dowel has been pulled out of it's hole. And since the glue is stronger than the wood, the wood broke when the dowel was pulled out. And there was glue on the whole dowel - solid dowels, not those with spiral or fluted grooves. It is very clear that the failure is not due to poor assembly or poor glue application.

So I started analyzing why that happened, which led me to realize that there just wasn't enough glued surface area to withstand the tension forces. Then I analyzed the surface areas and realized that only half of the dowel is getting glued to long grain.

What other people do when they build furniture is up to them. For me, it's easy to see that two dowels on the back of a chair seat is not strong enough and that a M&T in place of that will be stronger. The mathematics I provided will tell you how much stronger.

Mike

I think at this point we can just agree to disagree and build according to our own method preferences.

Edwin

[Patrick Walsh]

Figured I’d add to this being I have been working with dowels the last week.

I’m making the interior frames to what is referred to as “the case” for a pipe organ. It houses the internals, wind boxes pipes so forth and so on.

A drawing of assembly sans the actual functioning parts of the organ.

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I have only used dowels a couple times before to make passage doors. Honestly I was not impressed at the time as it felt slow and not precise at all even trying as hard as you could. Getting the two pieces to mate perfectly flush in any direction seemed impossible. Now close enough is easily obtainable but I’m not much into close enough.

So the new boss specified dowels to hold the internal frame together. The frame then gets wrapped in 7/8 thick bead board on battens and screwed to the frame.

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And the front and back frame done. The four sides will be attached with countersunk #12 scored indexed on dowels or dominoes.

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This time around I found getting alignment side to side and front to back a bit more easy but still not even close to perfect. A quick sand does take care of flushing up any joints but honestly that’s not my style. I find having to do such kinda hackish and largely a big waste of time vrs getting the joint setup well off the machine. In the case of dowels I feel that’s impossible. At least with a hand held dowel jig.

[Patrick Walsh]

I have used the small domino for years now. And again honestly I found the machine a bit disappointing mostly regarding alignment. Suggest so much to a domino advocate and you had better look out as the domino seems to be the holy grail. It’s fine enough and useful for general production type work but again it’s just a glorified biscuit jointer with a bit of added strength in the case of the small domino. At least that’s my opinion.

Again I’m a actual joinery guy and not “cope and stick” actual M+T but you know I’m a professional environment nobody is paying for that anymore. You gotta be making one off pieces of furniture for those not concerned with cost. Those people are few and far between imop your very lucky if you find that clientele. Most I know that do work for pennies and somehow someway can afford to.

So this arrived. For years I have wanted to give this machine a go. Back when I first really got into Woodworking I was building some passage doors and the rookie in me fully believed this machine was the only viable answer. At the time I was like many not willing to spend the coin on it. Now honesty it feels quite a inexpensive tool by comparison to most others.

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My impression after making one of the side frames. Well the joinery snob in me hates to say it but this thing is sweet. Mind you I say “sweet” in the context of production work and making actual money to buy the other things I really want and feed myself. I don’t say sweet from a quality or pride in my work and or as a craftsman as any hack dummy could make about anything with a domino.

I still don’t like the amount of end grain glue joint is relied upon for my current application. Add a cope and stick to the joint and these giant dominoes and even I can’t argue that’s gonna be a strong joint even for a exterior passage door that I would think will last multiple decades before it fails with modern glue. It pains me to say so much but that’s my take away.

It’s also screaming fast by comparison to a dowel jig, slot mortiser or table saw setup to cut tenon. And maybe the most important factor to me and my achy breaky carpel tunnel ridden hands is the domino results in almost zero fatigue vrs hand drilling dominoes or dam pockets screws without a dedicated pocket hole machine. So for that alone for making money on someone else’s clock I’ll take it.

Again the craftsman in me that takes the utmost pride in my work and has a true love for Woodworking still has no respect for this machine. But I can’t argue with good enough and that the machine will make me or my boss money to buy me the other stuff I want and or need. The work will stand the test of time and that’s I guess enough to hand]g my hat on. Again I’m cringing admitting so much.

So skip the dowels. Get the full size domino.

Oh and I found it much more easy to operate than the small domino. As a result the alignment of my work pieces was pretty much spot on requiring only the lightest of sanding.

Not bad at all..

[Mike Cutler]

M&T vs Dowels?

I'm sorry, but a properly sized, properly executed, M&T joint is going to be stronger than a dowel joint. The emphasis is on proper size.
Every comparison test I've seen, has always been done using an undersized M&T joint to compare it to whatever other joint, or joinery system,it's being compared to. Dowel, biscuit, Domino, etc. All these "systems" and all of the type techniques have uses, but for strength, the properly sized M&T joint is extremely hard to beat.
The other systems and joints can absolutely make a glued mechanical joint stronger than the wood, or material being used, but if the discussion is about strength alone, the M&T joint wins, as long as it is properly sized and constructed.

[Andrew More]

I'm sorry, but a properly sized, properly executed, M&T joint is going to be stronger than a dowel joint. The emphasis is on proper size.

Okay, now I'm intrigued, what do you consider to be the proper size for a M&T? I've always heard the tennon width should be about 1/3 of the total width of the Mortise piece it's going into, but I'm unclear on height, or depth.

[Mike Cutler]

Andrew.

The rule, as I know it, is the rule of 3's.
A tenon is 1/3rd the width of the mortised member. It's length is 2/3rd's the width of the mortised member. Tenon width is 5 times the thickness of a tenon, before it is divided. The "Japanese" tenon is even longer. Just shy of the full width. of the mortised member.
If I am joining 3" wide, 4/4 stock ,for a cabinet door ,the tenon is 2" long, 1-1/4" wide and 1/4" thick.
There are many variations to the M&T joint to add strength. It is the foundation joint of wood working.