End grain glue joints are stronger?!?!?!?!

[chris carter]

We have all these joints specifically designed to avoid end grain glue joints. I can’t think of how many times I’ve heard that glue joints with end grain are horribly weak and worthless. Almost like there’s not even any point in putting glue there. And when an end grain joint is necessary, you are supposed to add glue blocks that are long grain to long grain to support the joint. I’m trying for the life of me to figure out what this guy is overlooking. Or maybe (as he proposes) the conventional wisdom about glue and end grain is just plain wrong?

https://youtu.be/m7HxBa9WVis

[Joe A Faulkner]

Fascinating. Years ago I built a blanket chest out of Red Oak with mitered corners on the lid. I did not allow for wood movement and I did not use any splines or keys in the joints. Just glued everything with PVA. The chest was finished with oil-based Poly. The chest has always been kept in doors. 16.5 years in nO signs of the joints failing. I guess the end grain to end grain strength is at p,any here.

[Scott Winners]

TLDW. I did some testing with west system epoxy using 105 resin with I think #207 special clear hardener. I did end to end, face to face, edge to edge, edge to face, end to face, blah blah, a bunch of test pieces, all in Doug Fir construction lumber. For some of the end grain peices I did one coat of epoxy into the end grain to seal the tubules and then did the glue up.

I gave all the test pieces to a guy from my church who had, at the time, a rambunctious four year old son. I told him I wanted them tested to destruction without hurting the kid. Just break all of them and bring me back the wreckage. All of the combinations that had end grain as one of the joint halves came home first, whether or not I had first sealed the end grain with a premliminary coat of glue. The mortise and tenon joint, and the face to face joint I sent them are still in service; the face to face in use as a pad under a jack for changing tires on the family's full sized truck with many hammer marks on it. Judging by the foot prints and shoe marks the MT joint is a low step stool tricky to balance on.

I have not done any testing with PVA glue. If a joint can't stand up to a four year old with a collection of Tonka toys, a deck 20 feet off the ground and a hatchet of his own, that joint is not strong enough for me.

Utter respect for Joe's joinery as above. Joe, would you turn a four year old loose inside that box with a hatchet?

[Warren Mickley]

This guy is way in over his head. There is a reason most people are better off copying classic designs than making up new ones.

The question is not whether an end grain to end grain is stronger than side grain to side grain, but how an end grain joined piece compares to a piece without a joint. Joining two pieces to make a wider board does not affect strength the way joining two pieces to make a longer board does.

Here is an example. Suppose we take two cut offs from the end of a board 1 inch long and 8 inches wide and glue them together to make a 1x1x16 strip. A strip like this is weak whether there is a glue joint or not. You can break it with one finger. It is not suitable for a chair rung, joint or no joint.

Now take two long grain 1x1x8 pieces and glue them end to end. So we have 1x1x16 with a weak spot in the middle. The fact that this is stronger than the first example is not going to help if we want to make a chair rung out of it. It is much weaker than a straight grained piece that has no joint.

We can get away with gluing to increase width because it is in a direction where we don't expect much strength to begin with. We design around the fact tht wood is stronger in one direction than the other.

[Erich Weidner]

That was very interesting to watch.

[Mike Henderson]

I didn't watch the video, but I know from experience that end grain glue joints do not hold as well as long-grain-to-long-grain joints.

Mike

[Jim Koepke]

To my way of thinking this video proves that the glue is stronger than the wood when the breaking force is going with the grain. It also demonstrates the glue is not as strong as the wood when the breaking force is across the grain.

In other words, it shows which way to orient wood grain for the best resistance to a load.

jtk

[Prashun Patel]

I agree jim. It speaks more to the weakness of cross grain wood than to the strength of the glue.

The older I get the more I appreciate The first paragraph of Warrens post.

[Erich Weidner]

I didn't watch the video, but I know from experience that end grain glue joints do not hold as well as long-grain-to-long-grain joints.

Mike


I humbly suggest you watch it. It does in no way advocate that end grain gluing is the new thing to do. Rather I found that it reinforced why we glue how we do for joinery.
Really this is a video about where wood fails under stress vs where glue fails under stress. Totally worth the watch.

It isn't going to change how you work wood. But for me it helped me understand why we work wood the way we do. :)

[Lee Schierer]

The video shows that a properly glued joint (glue applied to both sides of the joint) is stronger than the lignin that holds the fibers together, but not nearly as strong as the fibers themselves. It does not advocate switching to end grain joints.

[Stan Calow]

There is a whole long discussion about this video in the General forum. Don't read more into the video than the guy says. Its very simply about one way joints fail, and not about all conditions and situations.

[Jim Koepke]

I didn't watch the video, but I know from experience that end grain glue joints do not hold as well as long-grain-to-long-grain joints.

Mike


I humbly suggest you watch it. It does in no way advocate that end grain gluing is the new thing to do. Rather I found that it reinforced why we glue how we do for joinery.
Really this is a video about where wood fails under stress vs where glue fails under stress. Totally worth the watch.

It isn't going to change how you work wood. But for me it helped me understand why we work wood the way we do. :)

Honestly the video didn't hold my attention though to the end.

Even ideas that sound ridiculous can illuminate our learning.

jtk

[Erich Weidner]

Honestly the video didn't hold my attention though to the end.

Even ideas that sound ridiculous can illuminate our learning.

jtk

Lol. Well, maybe I just liked watching that machine destroy wood and to see how it broke. I was pretty entertained.

[steven c newman]

Maybe he was trying to make a Board Stretcher?


Just a thought....exactly what do you call the way a mitre joint is glued together? Aren't some of those end grain to end grain, or am I missing something?

[Jim Koepke]

Maybe he was trying to make a Board Stretcher?


Just a thought....exactly what do you call the way a mitre joint is glued together? Aren't some of those end grain to end grain, or am I missing something?

If one wants a strong mitre/miter joint it will usually have a spline or dowels to hold it together. Some may use corner blocks.

There is a workable board stretcher joint. It will turn a 12" wide board into a 10" or 8" wide board depending on how much it needs to be stretched.

jtk