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  1. #1
    Join Date
    Feb 2007
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    Default New Domino Joint Tests

    The latest Wood Magazine July 2007 has some destructive tests done using:

    1. True mortise and tenon
    2. Dowels
    3. Domino
    4. BeadLOCK
    5. Biscuits

    Tests were performed at Iowa State University's Structural Materials Testing Lab.

    In the shear test, the joints finished in the order they are listed below:

    1. True mortise and tenon 1017lbs
    2. Dowels 609 lbs
    3. BeadLOCK 541 lbs
    4. Domino 464 lbs
    5. Biscuits 187 lbs

    In the Pull-Apart test, these are the results:

    1. True mortise and tenon 2525 lbs
    2. Dowels 1866 lbs
    3. Domino 1486 lbs
    4. BeadLOCK 1170 lbs
    5. Biscuits 766 lbs

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  3. #2
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    Default

    July issue, it is not even close to June yet!

    Interesting results there, I am bracing myself for all the comments from Domino owners

  4. #3
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    May 2006
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    sydney
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    Default

    Although I'm eager to get the Domino, I 'm glad to hear that the Mortice and Tenon is still the gold standard.
    Zelk

  5. #4
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    Default

    I'll bite. Basically the test 'results' are rubbish. See this thread on FOG: http://festoolownersgroup.com/index.php?topic=845.0 . If you examine the pictures, you will see that, of the five joints tested, only the biscuit joint actually failed; the other joints remained intact, but the wood just beyond the joint area failed. So the test did not actually test the joints themselves to destruction. So giving figures on their relative strength is totally misleading.
    I believe that Wood Magazine will be inundated by abuse from outraged wood technologists for publishing such nonsense.

    Rocker

  6. #5
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    Jul 2005
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    Victoria
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    Quote Originally Posted by Big Shed View Post

    Interesting results there, I am bracing myself for all the comments from Domino owners
    Nope. We have already covered it in depth over at FOG.

    [Edit - Rockers on the ball - beat me to it]

  7. #6
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    Quote Originally Posted by Rocker View Post
    I'll bite. Basically the test 'results' are rubbish.
    So you are saying that Iowa State University's Structural Materials Testing Lab knows less about testing structural materials than a bunch of woodworkers with an agenda and a vested interest?

    Quote Originally Posted by Rocker View Post
    If you examine the pictures, you will see that, of the five joints tested, only the biscuit joint actually failed; the other joints remained intact, but the wood just beyond the joint area failed.
    How do you explain the order then? Did the wood "know" it had a domino instead of a tenon holding it?

    Quote Originally Posted by Rocker View Post
    So giving figures on their relative strength is totally misleading.
    I believe that Wood Magazine will be inundated by abuse from outraged wood technologists for publishing such nonsense.
    The figures are valid data. If you read the article, you would know that Wood Magazine stated that all joints except biscuits were adequate for the reason you stated. They also still chose the Domino as the "winner" despite the weak data. I suspect, like you, they wanted it to win.

    The facts are obvious. Out of the joints tested, the strongest joint is a true mortise and tenon and not by a small factor but by about a factor of 2.

  8. #7
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    Aug 2003
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    Iowa State University's Structural Materials Testing Lab knows less about testing structural materials than a bunch of woodworkers
    I know one thing for sure. If you want to do tests that actually prove anything, they need to be repeated many times. It's no good making one of each type of joint because there are too many variables. How well was the joint made? How good was the contact between the glue and the surfaces of the joint? Were there any structural weaknesses in the timber itself? A woodworker knows that no two bits of timber are the same. You can't treat it as though it's a man-made product. When they've done a hundred of each type and then collated the results, I would accept it as a scientific test. Until then, it's just Mythbusters psuedo-science.

  9. #8
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    Feb 2007
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    Quote Originally Posted by silentC View Post
    I know one thing for sure. If you want to do tests that actually prove anything, they need to be repeated many times.
    They didn't DO one of each test. I don't know the number they did, but if you look at the pile of joints, it was much more than one each.

  10. #9
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    I think ill wait for a more comprehensive and scientific testing of the 4 methods by our very own Better Homes and Garden team (or Scott Cam) teamed up with the Arts Department at Monash. I wonder if they will come up with the same results

  11. #10
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    if you look at the pile of joints, it was much more than one each
    Fair enough. I've only seen pictures of one of each lined up.

    Well, it doesn't bother me because I don't have a Domino and no plans of buying one. I find it a bit hard to believe that a dowel joint would test stronger than a floating tenon, given the number of snapped dowels I've seen in furniture.

    I've also seen the results of another test that showed the biscuit as second only to M&T. I still believe there are too many variables to be conclusive about it and only time will tell how all this Dominoed furniture will stand up.

  12. #11
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    I was a bit surprised re Dowels vs Domino. Do you know if it is 1 domino vs 1 dowel or 1 domino vs 2 dowels?

    Mind you 1486 lbs is still pretty strong.
    Visit my website at www.myFineWoodWork.com

  13. #12
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    Texaswoodrat,

    The fact remains that the test recorded the load at which the wood failed (mostly away from the joint); the lab did not use wood that was thick enough and strong enough to ensure that the joints themselves failed, rather than the wood. So the figures that they used to assign the relative strengths of the joints were irrelevant to that question. They merely reflected the strength of the wood used in the test.

    Some of the woodworkers who contributed to the FOG thread on these tests were structural engineers, who pointed out the deficiencies of the testing regime.

    I would expect a traditional mortice-and-tenon joint to be stronger than a domino joint, if the timber was a hardwood; but it strains credulity to believe that a dowel joint would be stronger than a domino.

    Rocker

  14. #13
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    Quote Originally Posted by Rocker View Post
    Texaswoodrat,

    The fact remains that the test recorded the load at which the wood failed (mostly away from the joint); the lab did not use wood that was thick enough and strong enough to ensure that the joints themselves failed, rather than the wood. So the figures that they used to assign the relative strengths of the joints were irrelevant to that question. They merely reflected the strength of the wood used in the test.

    Some of the woodworkers who contributed to the FOG thread on these tests were structural engineers, who pointed out the deficiencies of the testing regime.

    I would expect a traditional mortice-and-tenon joint to be stronger than a domino joint, if the timber was a hardwood; but it strains credulity to believe that a dowel joint would be stronger than a domino.

    Rocker
    Would be interesting to see a number of tests undertaken on a number of different strength/hardness timbers in geometrically varying tests and then compare.

    I would like to see the values when the dowel/domino failed rather than the timber into which they were inserted - otherwise you can get all sorts of corrupted answers dependant upon the geometry of the parent material and not the critical item - be it domino/dowel/biscuit

    Does always amaze me that people so readily accept something because it comes from a university - everything has limitations and constraints and they need to be clearly defined to get a propper appreciation rather than unqualified broadbrush statements of little value.
    Cheers

    TEEJAY

    There is a very fine line between "hobby" and "mental illness"

    (Man was born to hunt and kill)

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