Thread: Help: Keeping a pine top flat?

I would put a number of relief cuts along the length (underside) of the top at 50mm apart on the table saw at 12-15mm deep then add a 10mm edging all around to hide the cuts.

If you can flex the top enough to remove the cupping with finger pressure i'd be concerned about flex when the table is completed, ie someone always inevitably sits/stands in the middle of the table and before you know it they're on the floor. Dining tables can get away with thinner tops by using an apron or similar design to strengthen the top.

If your client doesn't want this you'll need to add a support on the underside that will add strength and also remove the cup.

So the flex isn't much, but it's there. Over the width of the table (600mm), the cupping is around 3mm, maybe a tad less. I just want to ensure it doesn't warp and start wobbling once the legs are fitted...

PS: I don't have a tablesaw. I don't have space for a tablesaw...

I would just tell them that this is what happens if they dont want any structure under their table and they can either live with it or allow you to screw some rect tubing on the underside.

If costs is a concern then taking time to route it in is probably not worth it. The tubing wouldnt have to go all the way across, maybe 400mm

Hi Toxxyc,

I think we all prefer to make stuff that satisfies our clients/recipients as cheaply as we can get away with. Many folks here often have to "get creative" to find a solution. Often, the weirder the solution, the better it is... at least, in my experience.

May we have some pictures? It's very hard to suggest solutions when we're flying blind. Also, what tools do you have access to? It will help us to make appropriate suggestions for your situation.

Also, how are you planning to finish the top? Varnish? Oil? Wax? Please let us know.

Cupping happens to us all, don't worry!

I had a cupped bench top (as many often are), and the cupping was horrendous... the middle was about 25mm off the table on 600mm wide plank. Unfortunately, it was 33mm thick and hardwood, so it took more than a little weight to straighten. So I clamped it down to a flat surface (my work bench in this case) to straighten it out, left it there for about 10 days. I then promptly varnished/sealed all the sides (top, bottom, and all edges) so humidity wouldn't warp it in the future. It wasn't perfect, but it only had about 1mm or so cupping/warping remaining.

The weather can also be a consideration during varnishing of cupped boards. If it's particularly dry, I varnish the inside (concave) side of the cup first, which stops the moisture escaping that side (keeps it somewhat stable) while the longer (convex) side of the cup dehydrates and shrinks... straightening the board somewhat. Please note that this can still take days or even weeks. Obviously, if you're in a particularly humid environment, reversing that idea will be better. If in doubt, flatten as much as possible for as long as possible (it also helps the wood to acclimatise to your local area), then seal it up quickly.

Like previous responders have said, if the table top flexes under finger pressure, that wood table top will flex and possibly warp under heavier (meal time) loads in undesirable ways. It sounds like the wood is too thin or too weak for frameless/apron-less designs. I get that your client is "budget conscious", but if you can find some way to reinforce the top, you'll find it is much better. If you have access to recycled materials, or re-purposed scrap as a cheap way reinforce it in subtle ways, then it'll be a much stronger, flatter table.

Always happy to come up with improvised solutions, but I think most of us need to know more to help effectively.

Good luck!
Hamish.

I have attached a drawing which should work for such a small top, apart from putting the Steel Angle to the back of the Apron you could also put lengths of it across the width of the table at whatever centres you like.

The Angle can just be surface mounted because it's hidden by the Apron, if you put a 5mm x 5mm rebate in the Apron this will help break the line between the two pieces of timber and further help in not showing movement in the future.

Table Top.JPG

Thanks for the responses, guys! Using angle iron was actually one of my ideas, as I can mount it into the wood with a single line being routed out, but I have the rect tubing on hand. Perhaps I can just build a small frame to mount to the inside, and I'll inlay it a little bit (maybe halfway), considering I'm routing the spots for the legs' mounting plates anyway. Oh and I love a router...

I'm very new to all this, I'm teaching myself as I go along (as explained on the intro thread), and I have very few tools at my disposal. I have a router (second hand Bosch with an issue), a set of battery drills (2 x Bosch Blue 18v), a random orbit sander (Bosch Blue 125mm), a belt sander, electric hand plane, circular saw, jigsaw and a few hand tools like a square, a very cheap (I didn't know better) chisel, and a few other things.

The pine top is getting a single coat of a penetrating light walnut stain before being finished with Woodoc 30, which is a polywax sealer. I have a slight dislike for varnish because of the "plasticky" feel it gives tabletops, but that's just me.

I'll take some pictures if I'm at the piece again. Today I just cleaned out the one spot with a few tiny gaps where the knots are so I can fill that with epoxy after the staining process is done. Doing this I noticed that the cupping sort of subsided a bit. It was quite obvious two days ago, but now we have slightly different weather and it's mostly gone. If I put the slab of wood on the floor (which is flat) or even if I run it against a straight edge (like my SS 1m ruler) I see the cup is barely 3~4mm high, so it's not a lot at all. It doesn't take a lot of effort to just slightly bend it into place as well, so I think a lightweight frame or even a few pieces of angle iron will have no issue keeping it straight.

Did you think about breadboarding the ends?

I haven't, no. I don't think it'll look good on a top that small? I'll make it look less like a table and more like a cutting board, I think. I'm not a huge fan of breadboard ends, sorry