Kevin's experience is the same as mine. Pocket screws & glue are a bear to take apart.But if youve ever had the need due to a customer change to pop out a stile on a faceframe thats already assembled and finished you'd see that simply removing the pocket screws and with a very small mallet and a light/sharp tap, the stile (end grain to long grain) pops free like a charm and comes out completely clean.
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Interesting observation, and completely contrary to my experience. When I have dismantled pocket screwed frames after a couple of minutes they almost always tear the side grain out. Perhaps the difference is in the wood species used?
I wouldn't rely on an unreinforced end grain joint as seasonal wood movement would likely break it loose over time, but despite my initial skepticism I have come to rely on pocket screws with glue for face frame joinery.
My granddad always said, :As one door closes, another opens".
Wonderful man, terrible cabinet maker...
There is no MYTH to debunk.
This is not a myth or folklore it's science, plain and simple. The properties of PVA glue, the structure of wood and it's orientation all combine to make it so that some joints are strong and some are not as strong. Woodworkers learn about this or should, very early on.
The beginning of the distortion comes by putting forward a false premise, to claim to have solved some type of problem or issue that needed attention.
His premise is that the common perception about end grain to end grain wood joints being weak is incorrect. Spoiler alert, they are.
Before you launch into a "scientific experiment" as many have called this, you first need to know if it's been done or if it's necessary to be done.
We already know the strength of PVA glues.
We already know that wood breaks with the grain easily
We already know that wood is difficult to break accross the grain
So what point does this testing prove?
He titles his video "glue myths" but mainly tests wood strength.He performs his experiments and presents his findings in a way that makes it sound as if there is something new to be learned, there is not.
I suppose I should say I learned nothing new.
Maybe this is all new to him and his subscribers, I don't know.
Sadly the number of people who liked this video for whatever reason continues to grow. Many of the positive comments have come from popular woodworking personalities and people who should know better.
I find the video and the discussions surrounding it disappointing, even my part in it.
Wood glue is to assist joinery not replace it, build wisely.
JMHO
They dont care about woodworking and they do know better but cash is king so they are fine with the masses following flawed practices as long as it fattens the bottom line. Spagnolo is in that string and should be the first one to be a voice of reason but he doesnt even know which end of a dovetail drawer the pins and tails go on so why would he care about flawed glue logic.
Sadly you just have to let the failures teach their lessons.
I, for one, learned that an end grain joint is stronger than the wood with the grain. I expected the end grain joint to fail in the glue but at a much lower load than the wood with the grain. If you already knew that then good for you. Having said that I'm not going to run out and use an end grain joint in a structural component but I don't think he suggests that. I don't find the discussion disappointing at all, two best way to learn are discussions and doing stuff.
I agree completely!
He actually points out the things we all know which is wood is very weak when stressed parallel to the long grain of the wood.
Based on everyone saying not to join end grain that I assumed it wasn’t “strong” .
However, what he did show is that an end grain to end grain joint is stronger than long grain to long grain joint. This means an end grain to end grain joint is equivalent to turning wood in it’s weakest direction.
Also, I will use glue for end grain to end grain because it does provide some strength even if I would’ve thought it was weaker than long grain to long grain. He showed it is actually stronger.
This doesn’t change the fact that long grain to long grain is the weakest direction to load wood. What he is showing is that an end grain to grain joint is only slightly better than loading the wood in its weakest direction.
The end result doesn’t change how anything is done. I wouldn’t put a narrow piece of wood in a place to carry any load that relied on the long grain to long grain strength. The end grain to end grain joint is still weak in comparison to the bending strength in wood’s strongest direction.
Last edited by Eric Arnsdorff; 09-10-2021 at 6:32 PM.
Well I thought the guy took extreme care to be objective and was super low key. As an engineer I thought his approach was well thought out and well instrumented. I can’t find a fault with anything he did and would encourage him to keep exploring. I for one would not have predicted his results. 10 out of 10 in my bool
I think the holistic view of this question would consider the strength of the wood around the joint as much as the strength of the joint. Both, incidentally, impacted by grain direction.
Comparing the strength of edge grain glue-ups to end grain glue-ups is an interesting question, but what matters is whether the joint is strong enough for its intended purpose. An edge grain glue up is stronger than the wood, so yeah, if a solid piece is strong enough for your bending loads across the grain, a glued-up panel will be strong enough too. The trouble with an end grain glue-up is that bending loads with the grain are often too high for a glue joint to take (e.g. you'd walk on scaffolding made from a solid long piece, but not the same piece made from two short sections glued end-to-end).
Be interesting to see if seasonal movement made any difference in his tests.
Most woodworking projects are engineered for longevity rather than ultimate strength. Traditional joinery provides longevity and it can provide demountability if it is planned in at the start.
This is a neat video, perhaps it is worth putting a little glue on the end grain in a long run of dovetails with wide spacing, but I would not think it wise to rely upon an end grain glue up that does not otherwise have reinforcement.
Last edited by Brian Holcombe; 09-11-2021 at 9:27 AM.
Bumbling forward into the unknown.
In which case, since the grain is all running in the same direction by definition, it shouldn't be an issue, right? But I think people are assuming the test applies to mitered end grain joints, which is not at all the point. He's testing the strength of the glue/grain orientation, not woodworking joints. I saw no recommendations regarding applying this information. The more interesting part of this to me is the verification that long-grain to long-grain is weaker, but certainly not enough to stop using that kind of joinery.
< insert spurious quote here >
I have the same thought. Not that I'll use end-to-end joints from now on but I didn't expect the breaking point in the video to be larger than side-to-side.
I doubt many of those here who "claim" there was nothing new here and are so critical of the video knew this as well; they just don't want to admit it.
Well I've known glue is stronger than side a grain joint for decades.
https://www.youtube.com/watch?v=84Bx8-xBCxg
I've also known that an end grain joint will break at the glue line.
Just as he showed in the video. Nothing new
This is just bad science.
“The wood always splits before the glue fails”.
What this should tell you, is that the breaking strength of the glue joint is higher than the breaking strength of the wood in that orientation (side grain) which is x,
”On average, end to side joints were about 20% stronger than side to side."
X + 20%
“End grain joints were the strongest joints of all”
There is no way to know if end grain joints are strongest due to the fact that the side grain test and the end to side tests both failed before the actual joint strength could be measured. All you know for certain is that end grain joints fail at y. You can not claim to know or declare which is stronger, since in two of the three tests to be compared, the testing material routinely fails before a strength measurement of the glue joint could be taken. All you can prove, is that wood glue is stronger than x or x + 20%.
You could say end grain joints, y are stronger than x or x + 20% but that’s it. Anything else is pure speculation.
There is no myth
Here is a good video by Stumpy that further explains the glue myth video. https://www.youtube.com/watch?v=dwLWmoGh59g