Woodworking joint torture test
Posted by The Woodworker on Oct 31, 2009
DaveatWOODmag аѕkеd:
Arе pocket screws stronger thаn dowels? Arе wide tenons stronger thаn narrower ones? Arе deeper dadoes stronger thаn shallow ones? Fοr thе “Wood Joint Torture Test” іn WOOD magazine issue #173, wе сrеаtеd аnd thеn dеѕtrοуеd more thаn 100 joints іn ουr quest fοr thе аnѕwеrѕ tο those qυеѕtіοnѕ аnd more. Thіѕ video shows ѕοmе οf thе joints wе brοkе.
For clarity on my earlier post: the plywood joint “tested” in the video is submitted to a torsion, and not to a shear, load. This is neither to suggest that torsion is the proper test method, nor that shear testing would have been more valuable. Meaningful testing would have also assured equal joint areas (the number of combinations of that, alone, would have made a huge library of material), joint lengths, etc. Again: this video DOES NOT represent the scientific method properly applied.
Everyone should realize this “scientific” testing is bull: Plywood dado joint strength isn’t measured in shear, but in torsion. A shear test would have had the joint parallel to the direction in which force was applied. Even if the outer edge of the plywood had been supported, the test would have been of plywood’s flexural modulus and structural integrity instead of the joint per se. Add to that the remaining methodological flaws, and all you’ve got is a meaningless video of failures.
yeha, and wouldnt the type of timber alos affect the result, like what if the timber isnt seasoned properly and the moisture content allows it to be bent easier
Interesting!
I am wondering how joints and glue react to sudden impact. I mean, nobody sits down in a chair this slow. Most stress-situations in real life are impact-like. It requires as whole different testing set-up, but it would be interesting, too.
What about a Lap Joint?
I agree with you, this was very neat.
this was intrigueing said max
Very nice test results. It,s nice to see something different about woodworking every now and again. Thank you for the posting.
LOL he said **** stress:)
No wonder that the wood fails before the dowls. The wood has been cut regardless of the direction of the fibers. Thats the pricipal problem. The Vikings did it in a better way. They didn’t use a saw to cut wood
They used axes to split it. Wood always splits along the weakest line.
i wanted 2 see some dope
what would be shear? pressing a downward force directly at the joint, rather that 6 or 8 inches away like in the movie?
Dovetails are stronger due to the inherent mechanical strength of the dovetail. By this method of joinery, dovetailing will last as long as the wood that its made of whereas a glued up biscuit joint will be subject to wood movement slowly breaking down the joint and ultimately the joint will fail.
I’m building a kind of trunk. What would be stronger just using screws with a **** joint or a box joint? anyone got any ideas????
interesting
the shear test is not in shear
It sure is but hide glue used for centuries is just as good if used correctly as evidenced by 200 yr old furniture, much of it never used glue for anything other than a secondary attachment.
Wow, only stress tests I’ve ever done with wood is with a unit in use under normal wear and tear – in the AF we used to do stress and ***** testing on equipment but that was to insure a fighter didnt fall on someone’s house. Boeing’s wing test recently on a carbon fiber wing is just as awesome to watch especially at the failure point – BOOM.
It’s actually glue made for attaching gorillas to other gorillas. But they should stop doing it anyway.
Are biscuit joints stronger than dovetails?
Would like some expert advice on this, thanks.
goog video. My son and I have quite a few projects we’re going to work on in the future, this helps. thanks for sharing the information…
people should stop making glue from Gorillas.
Yeah.. Kind of my thoughts too. I got some heavy, heavy books, but I supprot my shelves at both ends. Yeeehahhhh!
*runs out to buy some of them super dowels*
For Woodworking it’s Great Info. If I build a Cabinet, I doubt that much Stress would ever be Encountered, unless a Gorilla was inside, trying to get out !!!