Gluing Bits Of Wood Together.

I've heard this over and over and over and over. And it's always so controversial; "This works!" vs "It'll never work!" My experience has been the latter.

It's the old argument about gluing endgrain wood. There aren't many that say that gluing endgrain to endgrain is actually a solid way to join, nor that gluing endgrain into a longitudinal grain is all that much better. 

But for better or for worse, the whole topic has just had a mini revival with the video by Wood If I Could. She feels strongly that gluing endgrain onto anything else needs mechanical help, from wiggle nails, dowels, biscuits, tenons, or screws. I have to agree.

It all stems from a video two years earlier when someone else proved that it doesn't matter because glue is stronger than wood fibres. And - sort of - that make sense until I try an experiment or three. But people tried to interpret that video as saying that endgrain joints are as good as longitudinal grain joints - because glue. Yeah. So ya!

Stumpy Nubs also picked the actual point of the OG video - that glue is way stronger than wood. Because glue. But he also seemed to miss the point. I could glue a square centimetre of steel to the end of a block of wood, and another square cm to the side. I can tell you the the steel will hold, the glue will hold - but the piece on the endgrain will come off much more easily than the piece on the longitudinal grain.

Errrhem!

It's one of the tyhings I do - in my opinion, badly - but still something I'm working on improving in. So I dunno about great carpentry and woodwork. In fact, I don't even do mediocre carpentry and woodwork. But I've also been around the traps and this gluing issue has happened to me at times:

"WTFSM is going on with this *&%$!##* join? Why will it not stay glued? AARRGGHH!!!!"

The Flying Spaghetti Monster never answers me. 

Over the years I've come up with an inkling of why it happens that when I glue two planks side by side after carefully straightening and dressing the edges, they stay glued to the point that I can often split one of the boards before the glue joint will let go.

And conversely, no matter how well I dress the ends of two boards and glue them up, they tend to fall apart when I put just a little bit of pressure on them...

It helps to imagine what goes into trees  when they're making treewood. ("Treewood "- hat's a technical term from my old man right there, if I pointed at a tree and asked what it was, he'd say, in all seriousness, "why that, that's bird-sitting-tree-wood." But he really could tell lumber apart by the look and smell of it, dozens of different types. Made me feel a bit uneducated about woodworking, and determined to do more until I became a bit educated. Anyway - back to treewood.)

As WIIC says, trees need to get water and nutrients up their wood, or they woodn't (hehehehe yes pun intended) survive. So the fibres in a tree trunk run lengthways, from the roots to the crown. The tree has capillaries running the length of them. Capillaries, you can picture as thin long straws.

When we saw a log up, we split it lengthways as that's the way you get long planks. The planks have all these little straws running the length of them. This also makes planks strong in one direction, and carpenters and woodworkers spend all their time dressing the wood to show off the grain of those capillaries, and plan their projects to use the wood in the optimal orientation so that the project will be strong and look good.

But sometimes you have to join the end of a plank to something else and that's when the fights start. If you're in one of those fights right now, use this analogy:

The Bundles Of Straws

Imagine a piece of wood as a bundle of straws. In fact, take a bundle of straws, and glue them together side by side until you have a shape like a plank that's 10 straws wide and 3 straws high. Just one length will do. It was relatively easy to glue the straws together side by side like that because there's so much surface area along the length of each straw for the glue to stick to.

Now make a second, identical plank and let them both dry for a few days side by side. Now try to glue them together end to end... 

And that's it. The whole lesson. Gluing two straws together end to end is a damn sight harder to do, and has a damn sight less strenght, than gluing two very short bits of straw together side to side. Even if the glue IS stronger, it doesn't matter because you can break the tips off capillaries easier than you can separate capillaries glued side by side.