If you pay attention to the woodworking sphere on YouTube, you have seen a video by Patrick Sullivan called “Glue Myths: 1. End grain” (posted below). I have been a fan of Patrick’s videos for a while now (I highly recommend his DIY DRO video). Even so, I scrolled right past this video when I was first served it a week ago. I figured it was going to just confirm what I already knew: End grain glue joints aren’t a great idea.
Soon after the emails, Instagram DMs, forum posts, and comments started coming and coming, and I finally watched the video. I was wrong. The video did not confirm my beliefs.
First off, watch Patrick’s video:
Wow! Right? Patrick’s methods seem as sound as can be–although I’m sure a few engineers will argue otherwise in the comments below (please do!).
My thoughts and opinions are my own here, and they’re still being formed the more I absorb the video and think about it. In Patrick’s testing, end-grain to end-grain joints perform better than side-grain to side-grain joints. I have a hard time arguing with the methods, so I can’t argue with the results. But I think the online community is grossly overestimating what these results mean. I can’t speak for Patrick*, but I think he would agree that people are getting a little too excited about the possibilities afforded by a new world of end-grain to end-grain joints!
#1 – The results aren’t that surprising
Anybody who has ever seen a 7-year old karate chop a pine board in half knows that the wood always splits between the long grain fibers as opposed to across them. What Patrick’s video shows is just that, with two added data points; end grain to long grain and end grain to end grain.
If you look at the results from Douglass Moore and Tom McKenna’s joint test article in 2009, you’ll see exactly the same thing; joints almost always fail when the long grain fibers tear out. As they state in the article:
When we looked closely at how joints tended to fail, we found a clear correlation with our test results. The stronger joints forced their component pieces to fail by fracture across the grain or right at the glue joint (miter), while with the intermediate-strength and weakest joints, failure occurred by the splitting of one piece along the grain.
The strongest joints are joints that work cohesively with everything around to keep everything in place. In fact, Marc Spagnuolo posted a fantastic response video (around the 5:30 mark) that drove this point home nicely.
#2 – Over time, I think wood movement would make all of this moot
Wood is going to move across its width. You can’t stop it, so all of your newfound cross-grain glue joints that performed so well in Patrick’s video are not likely to perform that well after a year or two of movement. I really hope that Patrick sets aside a few of these blanks to test in a year or two. Even better, I’d like to see the performance of these cross-grain glue-ups on a larger scale.
#3 – I can’t remember a time I wish I could have gotten away with a butt joint.
For the same reasons I don’t use pocket screws as permanent joinery, I can’t imagine an instance when I would be using a butt joint in any piece of furniture I cared about. Joinery not only gives you the strength you need for long-lasting furniture, but it makes everything easier to assemble. If you’ve ever tried to keep a glue-laden board perfectly in place while applying the appropriate clamping pressure, you know that it’s almost an impossible task. Glue is slippery and those boards are going to move all over the place. Joinery holds everything where it is supposed to be.
Let me know in the comments below how you would use an end-grain to end-grain joint, because I can’t think of any examples.
#4 – I have to the rethink justification for my answer on solid-wood chess boards, but not the answer itself.
We actually had this podcast clip sitting here ready for… well… this, I guess.
In episode 222, we discussed a listener’s desire to make a solid-wood chess board. One of my main justifications for advising that they not do that is because of the weakness of the end-grain joints that would result. We came up with a few methods of working around the problem (rabbeting the joints and inlaying blocks into a solid piece) but after watching Patrick’s video, I’m starting to rethink this one particular use case for end-grain glue joints. In the end though, I still worry about wood movement eventually taking its toll on a chessboard. Patrick’s video really makes me want to try to build one though and I’m hoping to do so soon. Of course I’ll update the blog reading audience!
Like Marc said in his video, maybe we should all stop saying that there is no strength added to a joint by adding glue to the shoulder of a tenon or end grain of a dovetail. It’s almost cliche at this point, but almost everyone glues that end grain and then extols the pointlessness of it. There is obviously some, if not a fair amount of strength added. Is it worth the squeeze-out it will cause? Or is the answer like everything else in woodworking—maybe?
*Patrick, if you read this, we’d love to have you on the podcast to discuss your video! Email us ([email protected])!