Structural Dovetail

This is actually kind of cool and I’m more than a little amazed it worked…

I had a While I was working on another project, part of the grandfather clock became very warped. It looked a little off, so I measured it. Turns out it was off by a full quarter inch. Yeah.  That’s not good.

I started going over solutions in my head. I considered surface planing it, but that would be a lot of work and would result in a tapered board. WhenI put it in clamps, I was able to make it straight-ish, and that might work for the short term, but it would eventually go back to being warped. If only I could find a way to clamp it permanently. In a moment of pure stupidity, I thought maybe if I made a dovetailed top, that would hold it together. I’ve hand-cut a few dovetails before, but this would require a really high level of precision. When making a dovetailed box or carcase, youhave the luxury of “tweaking” a bit. This would have to be really damn close on the first try.

The reason it works is the magic of the dovetail joint. The “tails” part is angled, shaped like a dove’s tail.  This lends a LOT of strength to the joint. It’s commonly used in drawer fronts because the angled shape basically creates a wedge that won’t pull apart, not matter how stuck your drawers get. What I’m creating here is basically the same as 2 opposing drawer fronts that are constantly being pulled on. But the mechanical strength of the joint will keep it tight forever.

In fact, the mechanical strength is so great that, when I first assembled the joint, I didn’t use any glue at all. I was so amazed that it fit so well I actually considered not gluing it at all. I did end up disassembling the joint and adding a little glue, but it’s purely as insurance.

The first photo shows just how big the gap was. The other side of the spanner is locked in place. Hopefully the other photos give a good visual of the angle of the dovetail joint and why it locks it into place.

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One Response to Structural Dovetail

  1. Tricia says:

    I do love reading about your projects.

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