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Thread: Power and hand together (2): we have cases!

  1. #16
    Quote Originally Posted by Derek Cohen View Post
    Unnecessarily so, Mike. End grain to end grain is TWICE as strong as long grain to long grain glue ups.

    Regards from Perth

    Derek
    I think you have some incorrect information, Derek. End grain to end grain glue ups are the weakest joint you can make. Long grain to long grain is a strong joint, stronger than the wood.

    You better check your sources. Or do some testing.

    Mike

    [Maybe we have a definition problem. End grain is when you cut a long piece of wood. The wood at the end of that board is end grain. If you try to glue two boards together end-to-end, the joint will be quite weak.

    If I glue two boards together side-to-side, that is long-grain to long-grain and the joint is quite strong.]]
    Last edited by Mike Henderson; 05-03-2023 at 2:38 PM.
    Go into the world and do well. But more importantly, go into the world and do good.

  2. #17
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    Quote Originally Posted by Warren Mickley View Post
    I watched the video. It is pitiful that someone who doesn't understand the first thing about wood would arrogate himself an expert.

    The first thing is that wood has a strong direction and a weak direction. We depend on this strong direction when designing joinery, furniture and buildings. The test he should be doing is an endgrain to endgrain joint compared to no joint at all. In this test his joint would fail miserably.

    In a side grain to side grain joint we can join two boards without a great difference between the joined board and a solid board. An end grain joint is very different

    I'd like to see him saw a hickory shovel handle across the grain, glue it back together, and then try to shovel with it. And I can assure you that a shovel handle made with the grain going crosswise instead of lengthwise would not hold up, whether it breaks at the glue joints or in between.
    Hmm, did you watch the whole video? He did compare end-grain to end-grain joints with a sample piece with no joint at all, which of course was far stronger than any of the glue joints. I'm not sure anybody was making that claim.

    The experiments seem pretty well thought out and well executed. I think they demonstrate what he intended to demonstrate. Of course, there are other variables in the design of furniture that the relative strength of a glued joint doesn't take into account: seasonal wood movement over time, mechanical forces being applied both as static and dynamic loads, wild temperature and moisture fluctuations are the ones I can think of off of the top of my head. But in terms of simply comparing the different types of glue joints, it seems to me to be well thought out.

  3. #18
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    Derek: The case looks beautiful, as usual for you.

    With regard to miter gluing:
    Sidegrain glued joints are stronger than wood is in that direction, or pretty weak. Endgrain glued joints are very weak compared to the grain in that direction. These things have led to standard joinery approaches that allow appropriate strength over time. People have overstated the differences at times, presumably with the intent of encouraging consistently good results.

    Patrick Sullivan has shown that some endgrain joints, tested soon after their assembly, are twice as strong as similar sidegrain joints. It would not be reasonable to ask him to test the number of samples, configurations or ages of joint to tell whether his observation is broadly applicable. Because of wood grain strength anisotropy it does not matter for most traditional joints, but miters may differ in that regard. Sidegrain miters are glued with alignment as the only reason for additions. Sullivan suggests endgrain miters should be similar or better. Splines definitely add glue surface, and can add fibers directly across the join. Presumably that's a stronger joint, but as usual the question is whether the extra strength is needed in a given application.
    Last edited by Alan Schwabacher; 05-03-2023 at 5:26 PM.

  4. #19
    Quote Originally Posted by David Carroll View Post
    Hmm, did you watch the whole video? He did compare end-grain to end-grain joints with a sample piece with no joint at all, which of course was far stronger than any of the glue joints. I'm not sure anybody was making that claim.

    The experiments seem pretty well thought out and well executed. I think they demonstrate what he intended to demonstrate. Of course, there are other variables in the design of furniture that the relative strength of a glued joint doesn't take into account: seasonal wood movement over time, mechanical forces being applied both as static and dynamic loads, wild temperature and moisture fluctuations are the ones I can think of off of the top of my head. But in terms of simply comparing the different types of glue joints, it seems to me to be well thought out.
    I think it is misleading to suggest that end grain joints are as strong as side grain joints because we expect so much more from our timber in the lengthwise direction.

    Suppose you wanted a panel for a case side that is 18X28. If you had two 10 wide boards they could easily be glued together to make a sturdy panel.
    If you had two 15 inch long boards you could glue them together, but then your panel would be weak in both directions Unsatisfactory.

    Or if you wanted a 16X60 bench seat, are you going to glue up two 30 inch long boards? It could make for some unhappy moments if two people were on the bench.

    Short boards glued end to end might work for karate class.

  5. #20
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    This is an interesting debate. Unfortunately I don't think it belongs in Derek's build post if we continue it. But I will add my 2 cents. I trust Derek's advice and have followed his work,tool reviews, tool mods, etc... for a lot of years. I integrate many of his methods in my shop every day. Having said this, I can't possibly get on board with end grain to end grain glue ups being stronger than long grain to long grain. I've done my own half hazard testing in my shop with this exact thing. I have also tested end grain 45deg miter joints. Without question the long grain to long grain is so much stronger than both of the other glue ups. But I do think many people give enough credit to how strong a miter joint on end grain can be without splines, domino's, biscuits, etc. As long as you consider the extra glue that's required so as not to starve the joint. End grain will always soak up much more glue than a long grain surface, which is the reason most suffer from failed end grain miter glue ups.

  6. #21
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    Now that I just watched the video, after posting above, I am a bit surprised. The only thing I disagree with is him saying the end grain glue up is stronger than long grain glue up. There is not a good way to test which one is stronger as the wood fails on the long grain glue up therefore there is no way to tell when the glue fails. The end grain glue up clearly fails on the glue line as the wood is much stronger when applying force that direction. But this doesn't conclude that an End grain glue up is stronger than a long grain glue up. The conclusion is that wood lignum is weaker than wood long grain.

  7. #22
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    Tony wrote:
    End grain will always soak up much more gluejj than a long grain surface, which is the reason most suffer from failed end grain miter glue ups
    .

    One omission from my post was the use of a sizing technique on the mitres. I always do this and just assumed all would know. Never assume. Sizing is the technique where the surface is coated with glue, where it is allowed to soak in and fill the tubes. When it is tacky, you add more glue, as if glueing for the first time.

    A second point is that mitres are not true end grain; they are also long grain. And remember, there is little stress on this joinery, unlike the extreme examples Warren would throw up to make his point. Come to reality: a bedside table or nightstand lives in a climate controlled room and has a gentle existence.

    Regards from Perth

    Derek

  8. #23
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    The video is chicanery. Garbage. He states end grain to end grain glue joints are always stronger than side to side glue joints. False. In the video he NEVER demonstrates failure of a side to side glue joint, only failure of wood ( not the glue joint ) when it is stressed along the grain of the wood. Thank you Warren for sniffing this one out. What would we do without you?

  9. #24
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    Quote Originally Posted by Tony Shea View Post
    Now that I just watched the video, after posting above, I am a bit surprised. The only thing I disagree with is him saying the end grain glue up is stronger than long grain glue up. There is not a good way to test which one is stronger as the wood fails on the long grain glue up therefore there is no way to tell when the glue fails. The end grain glue up clearly fails on the glue line as the wood is much stronger when applying force that direction. But this doesn't conclude that an End grain glue up is stronger than a long grain glue up. The conclusion is that wood lignum is weaker than wood long grain.
    I agree Tony.

  10. #25
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    Please really watch the video!
    His side to side joints do NOT break at the glue line, EVER. It is the wood that fails. So yes; long grain to long grain is the strongest joint. The only glue joint he tests is the end to end, which FAILS at the glue line.
    The other joints fail in the wood, the failure is a product of grain direction and flexion of the wood!

    He is NOT really testing glue lines at all because to do that he would have to use far stronger wood so they all failed at the glue line for comparison.

    This video is one of the most stupid contrived crap videos made by a non-engineer with NO brain.

    Yes I’m a classically trained scientist that did University physics in high school. Also an engineer.

    For those still struggling:
    The weakest GLUE joint is end to end, this video proves it. The rest is garbage.
    ​You can do a lot with very little! You can do a little more with a lot!

  11. #26
    Quote Originally Posted by Derek Cohen View Post
    Tony wrote: .

    One omission from my post was the use of a sizing technique on the mitres. I always do this and just assumed all would know. Never assume. Sizing is the technique where the surface is coated with glue, where it is allowed to soak in and fill the tubes. When it is tacky, you add more glue, as if glueing for the first time.

    A second point is that mitres are not true end grain; they are also long grain. And remember, there is little stress on this joinery, unlike the extreme examples Warren would throw up to make his point. Come to reality: a bedside table or nightstand lives in a climate controlled room and has a gentle existence.

    Regards from Perth

    Derek
    With a 45 degree miter, you can think of the joint as 50 percent end grain and 50 percent long grain. The 50 percent end grain is a weak joint, and the overall joint is weaker than a long-grain to long-grain joint. And, yes, I know about sizing and I assume most other people do, also. An end-grain joint is still weaker than a long grain joint, even with the sizing.

    The lower the angle of the joint (such as a scarf joint) the stronger the joint will be. The weakest is a 90 degree (flat to flat) end grain joint.

    The fact that a bedside table lives an easy life only means that a weak joint will work for it.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  12. #27
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    For those still struggling:
    The weakest GLUE joint is end to end, this video proves it. The rest is garbage.
    At the risk of being a broken record, we are discussing glueing mitres, not boards end-to-end.

    Regards from Perth

    Derek

  13. #28
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    Well this thread went off the rails.

    Thanks for posting this build Derek, I always appreciate the effort you put into showing how you do things, and I often pick up something worth remembering for later use.

  14. #29
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    It seems to me that the question is not which glue joint is strongest, but is the joint Derek selected strong enough for his application? Derek believes it is and the video (which I have not watched in a long time) would suggest it likely is if it is well executed.

  15. #30
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    Derek the difference between mitre grain and end grain contact area is trivial. The increase in surface area of the mitre is the main benefit over an end grain joint.

    A mitre spline and it’s alignment is a lot of work. Double blind dovetails are even more work. I can see the appeal of tape to align but what is the point when the joint will eventually fail?

    Glue does not replace a mechanical joint it just locks a mechanical joint in place.

    This is one example where a strong dovetail joined case that is then veneered works well.

    That ridiculous video should be stricken from this site, it is an abomination for real woodworkers.
    ​You can do a lot with very little! You can do a little more with a lot!

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