Keyed Sliding Dovetail

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Well well well, have a look inside the mystery joint from yesterday, sans shachi-sen. Look familiar? I’ve seen this joinery used to great effect by Chris Hall in numerous furniture pieces now (as well as larger structures like a gate), connecting things like table leg rails to the top frame above it. I found it to be quite a challenge! But, seeing as this is the way that I want to hold fast together the matched wooden straightedges for the study group meetup today, I thought it was high time to give it a go.

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The pieces to be joined are marked together with marking knife  for the two mortises, ensuring that they will match up when the dovetail keys are installed.

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The proportions of the dovetail are largely determined by the width of the chisels that will be used, adjusting the taper of the dovetail key is done by changing the mortise depth.

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A lot of the accuracy of the method that I use depends upon accurate depth to the mortise. Perhaps a more forgiving method would employ scribing the dovetail key to the slot that is cut. I layed out half of the dovetail key to make sure the proportions look good, and then made a small depth gauge to match.

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The bottom of the dovetail key is 1/2″, the top 1/4″, each slot is the same length at 3/4″. The bit that the dovetail key slides into starts as a 1/4″ wide mortise.

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And then the sides are flared out to meet the bottom, forming the dovetail slot. The back of these small sliding dovetails was very tight, I found myself needing a small fishtail chisel, unfortunately I don’t have one that small, so I resorted to a small 1/8″ detail chisel to clean the end grain corners as the cheeks of the dovetail slot were pared.

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My dovetail keys, both slightly over sized in every dimension. I made a small saw cut to define the depth of the waist.

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And then started splitting off the waste by paring top to bottom.

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Now a bit more accurate chisel work to make sure my surfaces are flat. I was pleased not to need a clamp to work these small pieces, though my fingers were at times in danger of poking with the chisel.

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The wedge was first fitted to the 1/2″ dimension of the mortise, undergoing a bit of adjustment here and there. By and large most of the fitting took place on the dovetail slot, especially paring in the back corners where I tended to leave too much wood.

I had to push down on the dovetail key pretty hard as I tapped it in with my hammer. I imagine a longer dovetail key would be easier in some respects to install without blowing out the face grain of the mortises. Tricky to fit these! Always a puzzle to figure out where the surfaces are proud.

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Each side of the dovetail key was individually fitted to its respective slot, so everything had to be labeled or its a fools progress. With the dovetail keys tapped home the plugs can be planed to fit from the same stock the keys are made of.

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I screwed the surface quality of the inside face by sawing too close while making the plug flush. Its always some stupid little error committed after jumping the more difficult hurdles, but that is why this is a practice attempt, I’ll be more mindful in the future. Which is to say, cut proud of the surface and pare with a chisel. Make your mama proud of your work!

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And how about we throw a locking wedge in there for full effect. This would be the full expression of the joinery application, and is what I plan to use to join the carcass to the bottom skirt of the cabinet piece I’m working on. I eyeballed the taper and transferred marks across the top of one piece, though the marks could also be brought across the interior surfaces once the pieces are separated.

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Definitely locked together, and easily demountable. Is it worth it to join pieces together this way as opposed to screws which are cheap and easily employed? I don’t know, but it sure is fun! You have to do work that you are satisfied with, and I for one will always seek to improve my technique.

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