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Sliding dovetail raised panels

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Forum topic by blackwell posted 11-04-2014 06:41 PM 1409 views 0 times favorited 6 replies Add to Favorites Watch
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blackwell

10 posts in 939 days


11-04-2014 06:41 PM

Topic tags/keywords: sliding dovetail wood movement

I’m planning a small entry table to sit at my front door. The rough size is 18” x 18” x 30” tall. I want a 12” tall cubby under the top by omitting what would be the front apron. The top half of the cubby may get a drawer. The legs/rails will be cut from 8/4 stock milled square.

Now I had this crazy(?) idea to do the whole thing w/ sliding dovetails. The three panels would be dovetailed on all sides and slide into their respective rails/stiles. The stiles (legs) will have a stopped sliding dovetail down to the bottom rail. It means I’ll have to assemble it in a certain order, the panels will have to slide into both top and bottom rails and that whole assembly will then slide into the legs.

I’m contemplating this joinery because I know it will be unbelievably strong but I’m starting to be concerned w/ wood movement. Unlike a floating raised panel there will be absolutely no allowance for seasonal movement on those panels. The panels will be < 12” x16” and made of 4/4 cherry. I see this joinery technique used on bookshelves but then they’re only joined on two sides and since wood moves mostly tangentially/across the grain it has room to move in the sliding dovetail.

Hopefully I described it clearly enough. I’d love to hear other’s thoughts on this. Should I consider a tongue and groove assembly on the panels?


6 replies so far

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bondogaposis

4032 posts in 1816 days


#1 posted 11-04-2014 07:07 PM

there will be absolutely no allowance for seasonal movement on those panels.

I am having a lot of trouble conceptualizing what you are trying to do based on your description. However based on the above quote, the panels will crack. They will move and if you don’t allow for it something will give.

-- Bondo Gaposis

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blackwell

10 posts in 939 days


#2 posted 11-04-2014 07:23 PM

Thanks for the input. As for what I’m trying to do, imagine a table like this http://www.sheeshamdirect.co.uk/wp-content/gallery/telephone-table/telephone-lamp-table.jpg where the panels around the sides and back are attached to the frame with sliding dovetails instead of a traditional t&g joint.

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Loren

8309 posts in 3113 days


#3 posted 11-04-2014 07:49 PM

They aren’t needed. Sliding dovetails are sometimes
used for table skirts. They resist racking very well,
even better than mortise and tenon, imo.

You might consider half sliding dovetails if you
want to play around with this notoriously finicky
joint. You can fit the flat side of the half
sliding dovetail with a hand plane. It’s described
in Gary Rogowski’s books on joinery.

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bondogaposis

4032 posts in 1816 days


#4 posted 11-04-2014 08:38 PM

It looks to me from the picture that the grain orientation of the panels are horizontal. Your concept could work if you don’t glue the panels and give them some room to move.

-- Bondo Gaposis

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bobro

308 posts in 775 days


#5 posted 11-04-2014 09:33 PM

I see what you’re saying, blackwell.

At the heart of it, what you’re describing adds up to a compound version of a table skirt slid down into a stopped groove (long tail, you might say), which is not too common but is done and is good and strong, as Loren described above.

If you think about it, though, where does a skirt go when it’s moving with the weather? Up and down. The wood expand and contracts vertically, across the grain. If the skirt is a single board and the top is cleated to it, not attached to the legs, everything is good.

If your construction were made without glue, it would literally lift the top up and down a bit over the seasons, and the panels wouldn’t crack. But if you glue those rails in, in your plan, you’re going to have the panel, which is wider and moving more, trapped between two firmly fixed elements moving little. Unfortunately you can’t let the panel float between the rails as you’ve dovetailed it in. It will eventually crack, probably in a kind of buckling split.

What you could do to solve all these problems yet still retain the look, strength and joinery pleasure of your original conception, is to make the top and bottom of the panel t+g, floating glueless between the rails, but dovetail the ends of the panel and rails, as a single unit. Then slide the whole thing down into the legs, and these sliding dovetails you can glue. This means the panel must be the same thickness as the rails of course.

edit- heh, I think Bondo beat me to it as I was typing.

second edit- it wouldn’t really be t+g for the top and bottom of the panel, but long mortises, because you don’t want the sliding dovetail to have those gaps in it. In fact, you could do it in an old Chinese manner, and hold the unglued panel in with several spaced floating tenons, with mortises on both frame and panel. This is amazingly strong, I guess because the depth makes up for the lack of length you’d get with t+g. Also it’s fun easy with hand tools.

-- Lao Ma: You are so full of anger and hatred. Xena: Everybody's gotta be full of something.

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bobro

308 posts in 775 days


#6 posted 11-04-2014 09:47 PM

double post

-- Lao Ma: You are so full of anger and hatred. Xena: Everybody's gotta be full of something.

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