I wasn't so blown away by this video. I think there are a couple flaws in the logic.

First is that the video repeatedly states that this is a "joint strength" comparison. Actually it compares wood strength for long grain vs. joint strength for end grain glue up. The glue joint on long grain is nowhere as critical as the wood strength. In the real world you are building to allow the wood to move so that the wood doesn't split along the length of the grain, not to keep glue joints from opening. Glue joints opening is due to poor joint construction, not joint failure. I'm having a hard time picturing a situation where the leverage on the joint is a critical consideration in design, although there most likely are situations where that comes into play. Modern glues are amazing strong; the wood is almost always going to fail in long grain before the glue joint.

End grain joints, as the creator of the video states, are by there nature small. They are also more likely to incur leverage on the joint as two long pieces would be coming together on the short joint.....again in most typical situations. This creates more stress on the joint. As shown in the video in this case the joint fails, not the wood. Would you build a chair leg out of two 2" x 2" x 9" long pieces of wood end glued together to make an 18" tall leg? Think of the leverage on that joint. You would have no problem though bringing two 1" x 2" x 18" long pieces together to make the leg.

The second flaw in the argument is the amount of glue being applied to the butt joints. There was way more than the usual amount used here so that it could seep into the end grain pores. As such you really have to take the amount of glue used from end grain to long grain into account in the comparison.

I'm not saying that one should never use a butt joint. I'm just critiquing the video's argument. A very strong butt joint can be created by applying a thin coat of TB2 to both board ends, letting it dry and then scraping it flat to the board end with a chisel or cabinet scraper. Then a 2nd normal amount of glue on the joint and final clamp up will produce a tremendously strong joint. Even here though I've never left this as a stand alone joint in a final product, but rather just as an initial glue up in a multi-step process such as you might find in a brick laid glue up.

BH Davis

Hey BH,

Nice to see you on the WW again.

I was exaggerating my surprise. It's simply a logical limiting factors problem. We could have figured out the solution. But we were all taught the wrong answer.

It's quite simple.

We know that modern glues are stronger than the lignin(natural resin holding the wood fibres together).

Edge to edge always breaks next to the glue line.

Good butt joints break the lignin in the edge grain. That demonstrates that the glue bond to the end grain is also stronger than the lignin. It does not show how much stronger.

We never bother to do the end grain joint test because we've been taught that its not strong. The reality is we already knew from the butt joint test that end grain glue joints are actually stronger.

That was interesting, always interesting to question our assumptions

In reality though as Bernie points out where is this an issue

Most joints are cut as much for indexing the material as for perceived strength