Woodworking Joint Tests
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In this video we test the shear strength of a variety of woodworking joints.
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When we are making a variety of woodworking projects it is not uncommon to wonder about joint strength, after all it might be something like a kitchen chair or a dinning room table and they need to hold a certain weight. There are many woodworking joints that can be used from simple butt joints, mechanical joints like pocket holes, and all sorts of wood joints like biscuit joints, mortise and tenon joints even dowel joints. All of these have differing strengths and the kinds of woods makes a difference too. In this video we pick some of the most popular joints, connect them with standard Titebond II glue, allow them to dry for a couple of days then tested each of them, and this video is the result of those tests.
This was a great test. Thanks for making it and sharing your results. The more of these I see, the more impressed I am by the dowel joint.
Can you do another video about reinforcing miter joints? I want to put the spline / no spline argument to bed!
Would be interesting to see a doweled lap, and mortise joint tested. As well as a glued pocket joint if it wasn’t glued already. Thing is if you did this is larger materials like 4x where the dowels and mortise have more supportive material I wonder how much stronger they would be compared to these others.. I’m guessing the lap joint did so well cause there is so much cross long grain to the glue up? That one really surprised me though
how are these joints made……. i want to learn how the are made
in my country its call "PURUS"
I was really hoping to also see the domino joint.
If you notice, the butt joint did not fail, the wood failed. (2:04)
What kind of lap joint did you use?
Thanks for making this video! I’m trying to decide on what to do for an articulating leg and this information is very helpful. I think I won’t use exactly the same joint as in the video. However, I feel the information is still relevant.
Fantastic video.
I would love to see the difference it would make if you put the pressure across the face – like a shelf.
Thanks for sharing =D
The pocket screw join didn’t fail at all. It held so firmly it broke the underlying wood. You can see that clearly in the slow mo. The joint remains in and square.
A few years ago a woodworking magazine reported on a test from a major
mid-western university (I apologize, I don’t remember the name of the
magazine or the school) and they came up with the same conclusion as yours.
Their half-lap was at the end of their boards and not at the middle, as
was yours. Their study showed the half-lap to be stronger than a mortise
and tenon or a bridle joint; here’s why. I think we can all agree that a
glue joint is stronger than the grain of most woods. In other words, if
we stress a glue joint, the grain will separate somewhere adjacent to
the glue joint before the actual glue joint fails. A glue to WOOD bond
is a very strong bond. A glue to GLUE bond is a very weak bond — much
like peanut brittle candy. Hence, if we could get a single molecule-thick layer
of glue, we’d probably have a stronger joint. That’s why a
half-lap is stronger. You can clamp a half-lap with much greater force,
thereby reducing the number of glue to glue bonds. We can not compress a
mortise and tenon joint very well because the mortise edges will not
collapse sufficiently. I suspect a bridle joint would be somewhere
inbetween since we can sufficiently clamp the open
ends but not the closed end. So those of you who keep piling on the glue
and squeezing it out, claiming you’re getting a better glue joint,
— you’re not. This would imply, there’s no such thing as a
"starved glue joint" as long as you have complete coverage of the mating
surfaces on well prepared boards. These comments are based on the use
of non-gap filling white or yellow glue, such as aliphatic resins–
PVAs. To get a better glue joint, spend more time preparing the surface
instead of just "using more glue" The smoother the better.
were the pocket holes glued?
you forgot a.wedge connection
Where the dowels used the kind that you cut yourself to various lengths from a long dowel stick?
Great video. Thanks. DD
When I first saw a biscuit jointer I felt it was a novelty and probably a passing fad that will be obsolete within a year. I’m surprised they’re still so popular. There’s no way I’d invest money in the equipment to do this when it’s good for nothing else and the final joints seem even more of a bodge than dowels.
What are the usual stresses on a joint in a normal piece of furniture ? Maybe a few pounds.
It’s been five years but this popped up in suggestions.
@WoodWorkWeb why have you not fixed your numbers here or on the article for the lap joint? It’s obvious that it was at 800, not 700. That’s an important distinction, especially since it wasn’t a full lap.
Helped me so much. Thank you sir for taking the tests.
Is this with glue or without?
So educational
test showed very good comparisons.
the 3 screws pocket joints were good enough for home furniture, if issue is not pocket visibility.
in fact test showed me using pocket screw joints combined with glue, would be perfect for house furniture.
pocket screw combined with glue would fair better in humid climates and would expansion ; specially when split, spring loading washer is used.
thank you from California.
You are an excellent woodworking teacher, one of the top three in YouTube…
Correction.. The lap joint went to 800 not 700.
Can you do a video for endgrain joints
Great info. Helps fill my lack of experience and knowledge in which joints to use and joint strength to expect. Thank you very much.
What I am convinced of is that none of these types of joints will ever really get pushed to their limits in the real world.
I seen a similar test with similar results
Very good test, no bias toward any one style joint. I wish you had included a domino and that you detailed the lap joint dimensions.
Oh boy, what great fun! Very interesting results and useful too. (And BTW I AM a structural engineer.)
Science! Makes joinery a little more selective now… Thanks!
Great tests.👍 It would be good if you could update and revise with a Festool Domino joint.👍
There are several misconceptions. None of the joints failed in shear, fail at the joints by bending. Shear failure would be failing by movement of the joint horizontally. Bending is the mode of failure.The joints left side is pulling up, tension. while the left side is in compression. Putting joint material at the middle of the vertical piece does not help because they are in the area of zero stress, so they little strength in bending. The joint will be stronger is the dowels are far left. The left side needs help at the very far left of the joint. A dowel or pocket hole close to the end will be stronger.
The pocket hole one looked like the wood underneath broke. Good to know pretty much any joint other than the butt one is okay.
Great video! I’m curious how a bolted joint with cross dowel would compare. I’m building a storage rack and want them open on the back so the joint needs to take the diagonal load.. was the half lap at end of wood or in center?
I was just going to do these test myself but you just saved me 5 hrs of my life ill never get back. Thanks
Lap joint is the best. If it was full width, it might have reached 1000 pounds!
Thanks for the excellent video
You got balls being that close to that much pressure aiming for failure. Good video though.
This is a very good video. I star with pocket hole, now I use lap joints. I want to see more videos like this, very useful.
Although you have put your hydraulic cylinder close to the joint, it’s still somewhat above it, so you’re putting a side load on the joint — thus it is not getting a pure shear load. If the point of contact was higher, the values that you found would be less (leverage) and if you moved the contact point closer to the joint, the values would be higher. To get a pure shear load, you would need a board with the joint on both ends and then your hydraulic cylinder would need to situated so that it was providing an equal force along the enter length of the board. I do not think you would get the same sort of splits on the M&T and dowel joints that way. To so such a test though, you’re going to need a more powerful cylinder (or at least a gauge that goes to a higher value).
Great information but what I see in common with all these tests is that the joint is always aligned with the strongest direction of the wood grain. There 2 more joint alignments of practical interest but no-one seems to bother testing them. I presume that would be because they are of inferior strength. There are cases though where they have to be used.
The only thing different I wish about this test, I wish there were three test of each.
Damn I didnt know dowels were so strong
How about testing the Domino
Excellent tests. Thanks, just what I needed to know. Now that we have done some transverse testing it would be good to get results for some longitudinal/tensionional/pullout tests
Thank you
fair test so far.
Excellent, thank you Colin