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8

@bowlturner gives some excellent suggestions. Let me just add a few things: Be sure to use cauls. They are pieces of wood laid across the top of the boards being joined to keep them aligned (and to spread clamping pressure). Make sure to alternate the position of the clamps. Have some clamping from the top and others clamping from the bottom. If you don't, ...


7

The ideal 'fix' for this is probably to saw the table apart (yes I know, *gulp*) and flip a few of the boards over, But going with what you have, two very traditional methods that were used to help keep tabletops flat were screwing the top to battens on the underside and breadboard ends. As a solution to your current obviously the first is more easily ...


6

Well I would tend to use my biscuit joiner to join all the pieces. Try to avoid flat sawn pieces in the middle of the table top and if you have flat sawn lumber then make sure you alternate the orientation, you want one up and then one down etc it will reduce the overall cupping motion across the whole top. An alternate that could be done is to run the ...


5

Typically there will either be cross pieces underneath, or "breadboard ends", to keep a tabletop flat. Either way you have to allow for wood movement as the table expands and shrinks across the grain, which means the crosspiece gets attached in such a way that the top can slide relative to it, eg by screws going thru slotted holes. You'll notice that most ...


5

Are there any other options open to me? There is one other option that you didn't mention. You can build a "router sled" to flatten wide boards. This is basically two rails on either side of the board with a narrow platform that slides along them. A router rides on the platform, and the platform has a slot cut through it that the bit projects through to ...


5

Your best 'chance' is using moisture. Basically getting the wood 'wet' and straightening it, then letting it dry straight. Some woods and small bends might work with wetting/moistening the board. However, steaming the board is likely to be the most successful on the widest ranges of species and quality. It also is unlikely to be worth the extra effort vs....


2

As clarified in the Comments, the back panel is thick enough MDF that fastening in through from the back is viable and that alone will do quite a bit to resist any tendency towards sagging. If you want to stiffen the shelves still further there are various established ways of doing this for plywood that could be adopted here, e.g. the below: But the ...


2

You could stiffen them up by nailing or screwing a 1/2" x 1" or 3/4" x 1 1/2" hardwood strip across the underside of the front edge of each shelf.


2

The asked question: The Sagulator is the generally accepted reference for determining if shelves are going to be strong enough to support the expected load over the desired span. Your table is nothing more than a very deep shelf, so lets take a look: For your situation of a 29" clear span (36" overall minus 2 @ 3.5" 2x4), a 3/4" piece of Eastern White ...


2

With today's glues, a simple butt edge joint works just fine. The boards need to be jointed well (the edges very straight, and I like a slight hollow towards the center ensuring the ends are tight and don't gap in the future). Clamping cauls will keep the boards aligned (I make my own from fir 2x4's). There will always be a slight misalignment of the boards ...


1

Varnish will likely help but it won't completely negate issues with warping and twisting. There are many other things you can do to help: You are correct in that the key to stopping wood from warping is stopping moisture from leaving or entering the wood too quickly - wood shrinks around 1% in its width for every 3% change in moisture content (IIRC) and ...


1

So this is what I did. Added screws from the back for each shelf: Screwed a 2mm thick and 25mm wide Aluminum strip to the front of each shelf. I also put tension on the Aluminum so it would counteract the sagging (pressed downwards as hard as I could on the middle part while putting in the screws). I got them from my scrap metal heap, else i would have ...


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