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Thread: Glue Myths Video

  1. #1
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    Glue Myths Video

    For those of you who have seen this recent video I found it quite enlightening.

    https://www.youtube.com/watch?v=m7HxBa9WVis

  2. #2
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    Wow, interesting. Looking for the discussion to follow……

  3. #3
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    Yes, that was very interesting. Thanks. I wonder how different the results would be with glues other than PVA?
    Hobbyist

  4. #4
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    Fascinating!

  5. #5
    Interesting for sure. I think I'll glue up some end grain butt joints and see how/where they break. Just to see it for myself. Thanks for posting!
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  6. #6
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    Thank you for posting this. I thoroughly enjoyed watching it and was surprised by the results.

  7. #7
    His conclusion is wrong and unsupported. He says that the end grain joint is stronger than the long grain joint. He also says that the long grain glue-ups never failed at the joint. His data tells us nothing about how much force it would take to break the long grain joint. Further more, his square pieces are not representative of real world situations.

  8. #8
    Quote Originally Posted by johnny means View Post
    His conclusion is wrong and unsupported. He says that the end grain joint is stronger than the long grain joint. He also says that the long grain glue-ups never failed at the joint. His data tells us nothing about how much force it would take to break the long grain joint. Further more, his square pieces are not representative of real world situations.
    Please understand that Im not trying to be a wise guy by asking this. I think Im just missing something..... If the end grain glue up does not fail at the joint, doesnt that mean the strength of the joint is determined by the strength of the wood? If so, why would the strength of the long grain joint be different? It did not break at the glue line - the wood broke.
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  9. #9
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    I am grateful not to have been taught early on that end grain is inherently weak. Done properly, I would generally agree with the video. The main problem people experience with end grain, in my opinion, is that most don't let the glue soak in then reapply, instead they just apply a "normal" amount then end up with a starved joint because the majority of the glue got pulled into the end grain.
    Timberlight Designs

  10. #10
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    Quote Originally Posted by Jonathan Jung View Post
    I am grateful not to have been taught early on that end grain is inherently weak. Done properly, I would generally agree with the video. The main problem people experience with end grain, in my opinion, is that most don't let the glue soak in then reapply, instead they just apply a "normal" amount then end up with a starved joint because the majority of the glue got pulled into the end grain.
    Except that he did exactly what you said was the main problem that most people do. He didn't let the glue soak in and then reapply, he just applied a normal amount and glued it up.

  11. #11
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    I can only think of one design detail that requires end grain to end grain. Itís the bottom of a table legs.
    Never would I just rely glue. A dowel is what Iíve used in the past before I owned the festool domino.
    Everyone should do their own testing
    Aj

  12. #12
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    Hard to argue with those results! We've been had.

    Now when do we get to eat food off of coatings other than butcher block oil?

  13. #13
    Quote Originally Posted by Frederick Skelly View Post
    Please understand that Im not trying to be a wise guy by asking this. I think Im just missing something..... If the end grain glue up does not fail at the joint, doesnt that mean the strength of the joint is determined by the strength of the wood? If so, why would the strength of the long grain joint be different? It did not break at the glue line - the wood broke.
    The end grain joint did fail at the glue line. The long grain glue ups never failed at the glue line, so we have no idea how much force would be needed to break that joint. I suspect his experiment would have yielded different results if he had loaded the assemblies on edge in order to remove the weakness of the wood from the equation. Maybe if he had cleaved them apart.

  14. #14
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    In my experience, most furniture glue joints fail over time due to repeated expansion - contraction. The edge/end joints he shows will certainly fail this way. I have made countless picture frames with mitered 45 degree corners. Even before time for expansion contraction, drop it on the floor and the joint will separate at the glue line...hence the reason for splining joints. There are many reasons for end grain scarf joints and mortised face frame corners beyond endgrain joint strength. Most involve resistance to expansion/contraction shear forces.
    Last edited by Jerry Wright; 09-08-2021 at 4:52 AM. Reason: Spelling
    Jerry

    "It is better to fail in originality than succeed in imitation" - Herman Melville

  15. #15
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    (Also posted this on another forum discussing the same video)

    What seems to be missing from the equation is that and end-grain glued joint is stronger than short grain wood fibers. By testing all these using these small blocks, his small wood samples all have a small cross section of long grain wood. Would you ever try to use a shelf made with the grain running opposite to the length of the shelf? Not likely because the wood itself does not have it's strength in that orientation.

    It is my belief that he is not actually testing an end-to-end grain joint against an end-to-side grain joint, and likewise to a side-to-side grain joint. He is instead testing the joint, and the adjoining wood, which due to the short grain samples, are the points that are actually failing, not the joint, as demonstrated in his presentation.

    He showed that the long grain of the wood was much stronger than any of the joints that he tested, but never showed a joint that extends a sample in the long grain direction, joined by a side grain-to-side grain joint. He should take another of his samples and glue them face to face, using only 3/4 of an inch for his overlap to keep the size of the actual glue joint the same, and then test that against his other samples. I would be surprised if he did not come out with a much different summary.

    A better way to describe the results of his test would be, "An end grain to end grain joint is stronger than the strength of short grain wood fibers."



    Clint

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