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Thread: Strongest Joint

  1. #1
    Join Date
    Nov 2006
    Zushi, Japan

    Strongest Joint

    I was thinking recently about joint stregth and took a look at FWW to see what they had to say. I found the following test and poll.

    Here are the results from a Fine Woodworking test on joint strength using a hydraulic press. The press stress tested for racking on a 90 degree joint constructed of 3/4 thick x 2.5 wide x 8 long inch cherry stock. Placing the stock on an end-to-end diagonal and applying vertical force down to the breaking point of the joint.

    1. HALF LAP 1,603 lb.
    2. BRIDLE 1,560 lb.
    3. SPLINED MITER 1,498 lb.
    4. 3⁄8-IN. MORTISE & TENON 1,444 lb.
    5. 3⁄8-IN. FLOATING M&T 1,396 lb.
    6. MITER 1,374 lb.
    7. 3⁄8-IN. WEDGED M&T 1,210 lb.
    8. 3⁄8-IN. PINNED M&T 1,162 lb.
    9. 5⁄16-IN. M&T 988 lb.
    10. BEADLOCK 836 lb.
    11. DOWEL 759 lb.
    12. ¼ -IN. M&T 717 lb.
    13. POCKET SCREW 698 lb.
    14. DOMINO 597 lb.
    15. BISCUIT 545 lb.
    16. BUTT 473 lb.
    17. COPE & STICK 313 lb.
    18. STUB TENON 200 lb.

    And here are the results of a readers poll in FWW forum Knots on the the strongest joint

    1. M&T
    2. Half Lap
    3. Bridle
    4. Pocket Screws
    5. Floating tenon
    6. Other
    7. Miter

  2. #2
    Join Date
    Nov 2006
    London, Ontario
    What I have yet to see (and I've seen articles like this a few times) is a test/article on (a) how much joint strength is good enough, and (b) some way to test how joints last over time.
    There's usually more than one way to do it... ........

  3. #3
    Join Date
    Oct 2009
    Dennison, MN
    I don't see a finger joint. That creates an insane amount of surface area.
    "Do, or do not. There is no try."

  4. #4
    Join Date
    Nov 2006
    Villa Park, CA
    I notice that the single criterion for the lists is strictly strongest joint, and if it is defined very specifically, you can test to that criterion and get your answer.

    I think the FWW poll came up with different answers because people factor other things in. The mortise and tenon may not be as strong as a half lap but the M&T looks better than a half lap, in most people's eyes, so they favor it.

    And people should factor in other things besides just the strength. As Art pointed out, once you have a number of joints that are "strong enough" you need to make your choice from that group based on other factors. And that's where the M&T wins out.

    Last edited by Mike Henderson; 03-05-2010 at 07:48 PM.
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

  5. #5
    Join Date
    Oct 2006
    somewhere east of Queen Creek, AZ - South East of Phoenix
    If a half Lap is the strongest then what about a full lap joint..
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  6. #6
    Join Date
    Mar 2008
    new york city burbs
    so if a pocket screws holds 700 lbs, if I put 2 pocket screws in each leg of a chair, does that mean I will have a chair that will hold 5600 lbs?

  7. #7
    Join Date
    Oct 2006
    ABQ NM
    Quote Originally Posted by Don Baer View Post
    If a half Lap is the strongest then what about a full lap joint..
    It won't be as strong, since it doesn't have the help of the joint shoulders.

    Lap Joint

    Half Lap Joint

    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

  8. #8
    Join Date
    Feb 2008
    East Freeetown, Massachusetts

    I wonder how the loading was applied.

    I would love to see test results for sever common joints with different loads applied.

    Load types:
    Tortional (likely this is what was applied to the above tested joints)
    Tension (pulling apart)

    I have to agree with "How strong is strong enough" - then apply asthetics to the joint.

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