Woodworking Tips & Techniques: Joinery – Strength of Glue Joints

by Robert
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Woodworking Tips & Techniques: Joinery – So how strong is a glue joint compared to the wood it’s holding together? You’ll find out in this video clip. A WoodWorkers Guild of America (WWGOA) original video.

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  • Alon Tako
    July 3, 2016

    What happens when the glue line is perpendicular to the grain?

  • christopher tharp
    July 3, 2016

    I am planning on building a frame for a full size bed, can I just glue 3 (2×6)'s together for the posts?

  • donepearce
    July 3, 2016

    The break I saw was straight along the glue joint. Sure there was some tearout below, but the main fracture line was dead straight.

  • QQxC NeRo
    July 3, 2016

    true for longgrain to longgrain joints on most woods. if you glue longgrain to endgrain though its not as strong and if you use wood with  very small pores like maple it can happen that it breaks at the seam

  • Michael M
    July 3, 2016

    I don't think it's a good test to use to prove your point. There are lots of other ways to do it and find accurate results because you have way too many variables in your 'test'. 

  • Wood Wrathe
    July 3, 2016

    To anyone that is doubting the glue strength.  Try laminating up 1/4" strips with glue rolled out evenly on all the surfaces.  Let it dry overnight and try to break the board.  It will be a lot stronger and than a full plank.  But it is made out of lots of skinny pieces. That may be a better way to prove the point to the doubters.

  • R.A.Y M.I.R
    July 3, 2016

    Could you tell me what would be the best glue…i am re wrapping my drum kit and i need some pretty strong glue witch would not come off aaaaaaaannnnd non corrosive:) thanks!

  • houdini0118
    July 3, 2016

    Screws and nails will still make the joint stronger as they extend farther into the wood than the glue does

  • Simon Baker
    July 3, 2016

    This is true, if you glue a saw-cut board together.

    If you have a properly jointed board though – edged on a surface planer, or even better, planed by hand, the glue joint will not break – the wood will.

  • Woodomain - Jeremy Broun
    July 3, 2016

    Precisely Brad – the point I make in my video about using Titebond glue

  • American Infidel
    July 3, 2016

    I feel like the test should be done by pulling the joint apart with force parallel to the joint you are testing.

  • lucylu40122
    July 3, 2016

    You doubters are nothing more than arm chair wood workers,glue up some boards and test them.

  • Daniel G
    July 3, 2016

    If you take two identical piece of wood and saw one in half and glue it back together, the cut one is going to be weaker than the solid one. This is because some of the grain that crossed that cut line has been severed, and now it's not continuous over the joint. Yes, some fibres pulls away on either side of the glue joint when it splits, but it still breaks pretty much directly down the glue line – if the glue wasn't creating a weak point in the board, it'd just follow the grain all the way.

  • timequakezombie
    July 3, 2016

    i think you missed hte whole point. wood will break. but he aimed it at the seam and it did not split down the seam but on either side. that is how wood is laminated, by gluing peices together. we are not talking about joints or end grain to end grain which is a whole other matter when it comes to moisture and movement and absorbtion in wood. i don't think you know a whole lot about woodworking with your argument you come off as quite ignorant in this matter.

  • timequakezombie
    July 3, 2016

    is glue enough for mitered cabinet doors, or should i be using biscuits or something else as well.

  • Brad Cox
    July 3, 2016

    Proof of what? Edge grain is already known to be weak. Try that again with end-grain.

  • Daveyhunter6
    July 3, 2016

    thanks

  • WoodWorkers Guild Of America
    July 3, 2016

    White glue has a longer tack time than yellow glue and will give you more working time to assemble parts.

  • yzhou88
    July 3, 2016

    You conclusion is misleading. Your result shows that the glue is not strong. Because it breaks along the seam, and always along the seam, that means the seam is the most weak part.
    My guess is that the glue has a chemical process of "melting"(or similar process) the board and then stick them together, the glue itself is strong.
    Think about this: you did not used too much strength to break it. So, if the board in your a hand is a solid one, NOT a glued one, then most likely it will NOT BREAK!

  • jfan4reva
    July 3, 2016

    Hmmm, I'd be more convinced if the panel hadn't broken along the glue joint for most of the length of the board.
    There's a reason why they split boards in the direction of the grain in martial arts demonstrations. It's because the wood is weakest in that direction. So this 'proves' that the glue is stronger than the wood in the weakest direction. Perhaps.
    Now glue two boards together end grain to end grain and lets see if the glue joint is still stronger than the wood.