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Forum topic by BalsaWood posted 02-15-2019 11:53 PM 671 views 0 times favorited 21 replies Add to Favorites Watch
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BalsaWood

110 posts in 1456 days


02-15-2019 11:53 PM

I’m a fan of mortise and tenon joints but I’ve used dowels for a couple small end tables. They seem to be pretty strong and are not that hard to setup but you have to be very accurate with them. I was browsing around for the strength of the joint and came across this:

https://www.canadianwoodworking.com/get-more/how-strong-dowel-joint

I’m curious on what other people’s opinions are on dowel joints.


21 replies so far

View Kelster58's profile

Kelster58

715 posts in 837 days


#1 posted 02-16-2019 12:08 AM

That’’s a pretty cool article Matthias Wandel did a pretty cool analysis too on Youtube. Here is the link. Turns out doing things the old fashioned way works.

https://www.youtube.com/watch?v=apsH8eBfjVA

-- K. Stone “Tell me and I forget, teach me and I may remember, involve me and I learn.” ― Benjamin Franklin

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ArtMann

1319 posts in 1114 days


#2 posted 02-16-2019 12:35 AM

What a Rube Goldberg type apparatus Matthias came up with! Why not just use a hydraulic jack?

In most cases, strength tests like these are not of much value. What you are measuring is whether the joint is 10 or 20 times as strong as it needs to be or just 2 or 3 times as strong as necessary. I use a lot of pocket hole joints even thought I know they aren’t as strong as dowel or M&T joints because they are good enough for what I need. Why waste time on anything more for something like shop cabinets?

I mostly use dowel joints where strength is important and I don’t want the fasteners to show even though I know M&T is stronger. Once again, why waste time?

Festool claims that the Domino floating tenon machine makes stronger joints because they compare 1 Domino to 1 dowel. They even published a video about it. I thought it was ridiculous. I almost never use just 1 dowel in a joint. If you have a good jig and use as many as you can fit in a joint, it is a lot stronger than a Domino joint. If Festool wants to impress me, they need to perform a more realistic test.

View ed13's profile

ed13

32 posts in 848 days


#3 posted 02-16-2019 01:29 AM

Here’s how it was explained to me: Imagine a classic M&T joining a rail and stile for a door. Look inside the mortise in the stile. The big surfaces that mate with the tenon cheeks are face grain and glue up strongly with the tenon cheeck face grain. The narrow sides of the mortise are end grain and, even though the corresponding face on the tenon is face grain, the glue-up isn’t strong in tension because of the end grain.

Now consider a rail joined to a stile with a dowel. The dowel is face grain all the way around. Look inside the hole in the stile that will receive the dowel. The sides of the hole (width-wise) correspond to long fibers and can bond strongly. The top and bottom of the hole (along the length of the stile) are pure end grain, and will bond weakly. All the surface area of the hole between these two extremes are somewhere in between pure long grain and pure end grain, so they are intermediate in strength. So, even if you make equal surface area, dowel vs. traditional tenon, much of the area in the hole has an end grain component and can’t be as strong as the classic tenon, which is a nearly perfect face-grain glue-up.

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BalsaWood

110 posts in 1456 days


#4 posted 02-16-2019 03:48 AM



What a Rube Goldberg type apparatus Matthias came up with! Why not just use a hydraulic jack?

In most cases, strength tests like these are not of much value. What you are measuring is whether the joint is 10 or 20 times as strong as it needs to be or just 2 or 3 times as strong as necessary. I use a lot of pocket hole joints even thought I know they aren t as strong as dowel or M&T joints because they are good enough for what I need. Why waste time on anything more for something like shop cabinets?

I mostly use dowel joints where strength is important and I don t want the fasteners to show even though I know M&T is stronger. Once again, why waste time?

Festool claims that the Domino floating tenon machine makes stronger joints because they compare 1 Domino to 1 dowel. They even published a video about it. I thought it was ridiculous. I almost never use just 1 dowel in a joint. If you have a good jig and use as many as you can fit in a joint, it is a lot stronger than a Domino joint. If Festool wants to impress me, they need to perform a more realistic test.

- ArtMann

Yep- if I do dowel joints, I use 3 dowels per joint most of the time.

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BalsaWood

110 posts in 1456 days


#5 posted 02-16-2019 03:52 AM



Here s how it was explained to me: Imagine a classic M&T joining a rail and stile for a door. Look inside the mortise in the stile. The big surfaces that mate with the tenon cheeks are face grain and glue up strongly with the tenon cheeck face grain. The narrow sides of the mortise are end grain and, even though the corresponding face on the tenon is face grain, the glue-up isn t strong in tension because of the end grain.

Now consider a rail joined to a stile with a dowel. The dowel is face grain all the way around. Look inside the hole in the stile that will receive the dowel. The sides of the hole (width-wise) correspond to long fibers and can bond strongly. The top and bottom of the hole (along the length of the stile) are pure end grain, and will bond weakly. All the surface area of the hole between these two extremes are somewhere in between pure long grain and pure end grain, so they are intermediate in strength. So, even if you make equal surface area, dowel vs. traditional tenon, much of the area in the hole has an end grain component and can t be as strong as the classic tenon, which is a nearly perfect face-grain glue-up.

- ed13

No doubt M&T is a really strong joint. Even better when pinned. It is nice to have such a variety of options for joinery. That is the great thing about woodworking. So many different ways of doing things.

View SMP's profile

SMP

456 posts in 203 days


#6 posted 02-16-2019 04:07 AM

Well keyed through dowel joints just don’t look that great.

View Fuzzybearz's profile

Fuzzybearz

84 posts in 367 days


#7 posted 02-17-2019 07:30 AM

I was told the festool domino is good because it takes the guesswork out of joinery. But yea, you should build your stuff with the stresses you expect to encounter. Alot of times I end up overscrewing, waterproofing, and finishing the underside of things when it’s not needed. Don’t be stupid like me.

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Tony1212

291 posts in 2032 days


#8 posted 02-18-2019 09:30 PM



Here s how it was explained to me: Imagine a classic M&T joining a rail and stile for a door. Look inside the mortise in the stile. The big surfaces that mate with the tenon cheeks are face grain and glue up strongly with the tenon cheeck face grain. The narrow sides of the mortise are end grain and, even though the corresponding face on the tenon is face grain, the glue-up isn t strong in tension because of the end grain.

Now consider a rail joined to a stile with a dowel. The dowel is face grain all the way around. Look inside the hole in the stile that will receive the dowel. The sides of the hole (width-wise) correspond to long fibers and can bond strongly. The top and bottom of the hole (along the length of the stile) are pure end grain, and will bond weakly. All the surface area of the hole between these two extremes are somewhere in between pure long grain and pure end grain, so they are intermediate in strength. So, even if you make equal surface area, dowel vs. traditional tenon, much of the area in the hole has an end grain component and can t be as strong as the classic tenon, which is a nearly perfect face-grain glue-up.

- ed13

Hmm, I see where you’re coming from, but I think you’re just repeating the same test as Festool that ArtMan mentioned in the post above yours. A nice thick tenon vs a single dowel.

If you size that tenon down to the size of a dowel, I think they would just about be equivalent in strength. If you look in the mortise/hole in the stile, you’d have end grain on top and bottom of the mortise/hole, but long grain on the sides and end. In the rail, you’d have long grain all the way around the mortise/hole and end grain only at the end of the hole which would be just as strong as a tenon of the same size.

And like ArtMan says in an earlier post, we only need to exceed the expected stress by a bit, 2 or 3 times vs 10 or 20 times. If you’re in a production shop, dowels are much faster than m&t are a significant cost savings with only a little compromise on joint strength.

That said, if you enjoy making m&t, by all means continue to do so. Have fun and enjoy the craftsmanship.

-- Tony, SW Chicago Suburbs

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ArtMann

1319 posts in 1114 days


#9 posted 02-19-2019 02:45 AM

Way back when i was experimenting with the strength of glue and glue joints, I found that the simple half lap joint is stronger than the M&T joints I made. The rail or stile piece would break before the glue joint. That was not true of M&T. I made cabinet doors that way back in the early 1980’s and I haven’t heard of a failure yet, although there could be. The problem with them is they are somewhat amateurish looking.

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ed13

32 posts in 848 days


#10 posted 02-19-2019 02:54 AM

@ArtMann what made them look amateurish? If it’s what I think it is, did you ever try a mitered half-lap? I’m guessing your half-lap divided something like 1/3 thickness against 2/3 thickness so that you could run a groove for the panel rather than being 1/2 thickness against half thickness?

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Woodknack

12638 posts in 2677 days


#11 posted 02-19-2019 05:58 AM

Weird that dowels are coming back into fashion, memories are short. They fell out of favor because they don’t hold over the long term but nowadays nobody keeps furniture long term so it probably doesn’t matter. The new fluted dowels might hold up better, probably will.

-- Rick M, http://thewoodknack.blogspot.com/

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ArtMann

1319 posts in 1114 days


#12 posted 02-19-2019 05:31 PM

Perhaps your dowel joints don’t hold up well but I started using them in 1977 and I have yet to replace or repair a piece I built with them. I have heard that dowels don’t hold up too but i have never seen any credible evidence of this. Can you please direct me to where I can investigate?

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WoodenDreams

505 posts in 208 days


#13 posted 02-19-2019 05:59 PM

+1 on ArtMann. Why not just build the joint to the purpose needed. I seen people frown when I’ve told them some of my joints are doweled, and give a nod when I’ve told them that this joint was made with mortise & tenon. Some have been surprised when I’ve told them the joint was a locking miter joint. The article didn’t mention anything about pinning a mortise & tenon joint.

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pintodeluxe

5883 posts in 3111 days


#14 posted 02-19-2019 07:16 PM

I think it’s interesting that the usual way to test joint strength is to glue up one joint, and bend it until it breaks. A chair or cabinet door would never have just one joint. It has 4 or 8 or more joints. Furniture failure is rarely from one peak force, but more often from repeated strains.

I don’t know a better way to test joint strength, but I look at old furniture that has come apart and try to see what failed. A cross-pegged mortise and tenon could have the glue completely fail, and it would still be a sound joint. When a dowel fails, it lets the joint open up. In a way, loose tenons are just flat dowels, albeit with a little more surface area. For me, it’s hard to beat the strength of an integral tenon.

Of course I do use biscuits and dowels occasionally, just not where a lot of strength is required.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View BalsaWood's profile

BalsaWood

110 posts in 1456 days


#15 posted 02-19-2019 09:41 PM



Weird that dowels are coming back into fashion, memories are short. They fell out of favor because they don t hold over the long term but nowadays nobody keeps furniture long term so it probably doesn t matter. The new fluted dowels might hold up better, probably will.

- Woodknack

I think they got that reputation from a long time ago from being used by furniture factories who didn’t use enough glue and didn’t do a good job using dowels. Modern glues and multiple dowels per joint are really strong.

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