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Accounting for wood movement in custom side-table/bookcase

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Forum topic by BB1 posted 07-08-2016 03:56 PM 526 views 0 times favorited 5 replies Add to Favorites Watch
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BB1

487 posts in 313 days


07-08-2016 03:56 PM

I am working on plans for a side table/book shelf for a friend. This project will be made from walnut from his century farm – thus, this is one of those projects in which the raw materials are pretty special. The dimensions are to be 30 inches tall, 30 inches wide, and 12 inches deep (although I’m thinking that a bit deeper would be more stable). The desire is to have three shelves, the top one divided into two equal sections. Below is the sketch he gave me (sorry – tried to figure out SketchUp but wasn’t having much luck with it). I’m hoping for some help with figuring out the joinery as this will be my first furniture item constructed entirely from wood (rather than a plywood with wood framing).

For the case, could I use blind dovetails to join the top/bottom to the sides?
For the shelves, I am unsure of the best way to allow for wood movement. I have seen a half dovetail used for shelving in a video (and question my ability to do that). Not sure if a cleat type system might work that would allow the shelf to be somewhat set (as the plan does not include adjustable shelves) but yet allow for the inevitable wood movement.

I’m sure these are basic questions but I haven’t been able to find answers in my google search. This isn’t a project I want to learn along the way – hoping to have my plan of action set so the end product is worthy of the materials. I appreciate any insights.


5 replies so far

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jdh122

879 posts in 2283 days


#1 posted 07-08-2016 04:12 PM

Bookcases don’t generally have wood movement issues, since the sides, top, bottom and shelves (and even dividers) all have boards that have the grain running in the same direction. The whole piece gets a bit deeper or shallower over the course of a year, but there are no issues. The sliding dovetail in this application is done because it is a strong attractive joint (especially if you do a stopped dovetail). A rabbet will work too, although you need some other way to attach the top and bottom.
The only way to get wood movement issues here would be to use a cleat system, since the cleats would have the grain perpendicular to that in the sides of the bookcase. Another potential area to look for in a bookcase would be the back: either use plywood or nail on tongue-and-groove or shiplap boards.
Personally I would steer clear of cleats as a means to attach shelves on a piece where you really want to honor the specialness of the material…

-- Jeremy, in the Acadian forests

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bondogaposis

4034 posts in 1816 days


#2 posted 07-08-2016 04:59 PM

Without cross grain construction, there are no wood movement issues, all the boards will move in unison. Don’t use cleats, they are ugly and are cross grain, so you will have to consider movement. Set the shelves in dadoes, it looks way better, is stronger and eliminates movement issues.

-- Bondo Gaposis

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BB1

487 posts in 313 days


#3 posted 07-08-2016 07:03 PM

Thank you for the help. If I might, a couple followups. Sounds like cleats weren’t a good idea so can use a dado instead for the shelves. Bondo – is there a recommended depth for dados, or is there a calculation for the length/thickness of the shelf that determines how deep to cut the dado? Once done, should this be a friction fit or am I ok to glue it as well?

I am not sure about how I will approach the back. I think this will be placed next to a chair so both front/back will be visible (rather than the back up against a wall). Thus, plywood would not be an option so will look up more on the tongue-and-groove or shiplap that Jeremy mentioned. If anyone has a project that used one of these methods, I would be interested in viewing.

Again, I appreciate the information. Hopefully will have a project post down the road with a successfully completed bookcase/stand.

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jdh122

879 posts in 2283 days


#4 posted 07-09-2016 12:55 PM

Definitely glue the wood in the dado. I don’t know of any rule of thumb for the depth of the dado. Shallower dados are stronger but leave less glue surface. In 3/4 inch sides I’d probably do 3/8 inch dados. Note that the length of the sides have to be quite exact.
I’ve done shiplap backs on various casework pieces, but never really take pictures of it, because it’s hidden. But I bet an online search will show you details. The fact that the back will be visible does not mean you can’t use plywood – rout a 3/16 inch rabbet into the sides and top and bottom. 1/4 inch plywood gets nailed in and is invisible from the sides and top. This will actually add more strength than the shiplap or tongue and groove, plus you can add nails through the back into the shelves for even more stiffening. Again, depends on the look you’re going for.
As I mentioned, you’ll need to use a different type of joint for the top and bottom horizontal pieces. Dowels will work, half-blind dovetails look nice on the top but are trickier. Plugged screws in from the sides are a possibility too, although I probably wouldn’t.

-- Jeremy, in the Acadian forests

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BB1

487 posts in 313 days


#5 posted 07-09-2016 03:03 PM

Jeremy – thank you for the additional help. Not sure if plywood or shiplap will be optimal – am thinking of trying some boards running across that would keep books from falling out the back but yet be somewhat open (i.e., maybe 3 inch boards with 2 inch gaps between). Then I run into how to attach those without fasteners showing. Will have to ask my friend what look he is wanting. Ideally, I would like it all be be from the walnut wood he has.

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