Hi all,
I’m looking to build a table top for a desk. I would like to avoid warping/cupping as much as possible. Is edge joining three 60” L x 9 1/4” 5/4 white oak boards with biscuits and glue good enough? Any wisdom that can help is greatly appreciated!
Replies
It will work just as good without the biscuits. Fastening it down properly will help.
But if the wood is wonky, or not dried well, it's going to do what it wants to do.
Edge jointing for the glueline is a good plan. More important for flatness is making sure each of the boards are dead flat before glueup. Biscuits will make alignment easier for glueup but will not add strength.
If you use them give the top an extra week to dry before final surfacing. The little pockets of glue in the slots add enough moisture to cause local swelling. If you sand out the bumps you'll have depressions after it dries out. (Don't ask me how I know.)
Thanks MJ. For 5/4 boards, will a single biscuit every 6” inches work? I’ve seen people also do a double biscuit slot so just wanted to make sure. Thanks
Biscuits do nothing for strength in this kind of glue up. Adding extras just makes things complicated, unnecessarily.
The only thing they can do here is keep the surface aligned. But if the biscuits are off a tiny bit, the top will be off by that much.
For alignment, put a biscuit 6 inches from each end, and one in the middle. Using more is not necessary.
Over a 60" glueup I'd probably use 4 at the most. put the end ones in maybe 6 inches to leave solid meat in case you decide to shorten the top as your build progresses.
a bamboo desktop?
I’ll be using 5/4 white oak
To minimize warping choose quarter or rift sawn wood. If you choose a cathedral pattern it will warp with humidity. Probably not enough to notice or affect table use. If you do use biscuits, set them more near the bottom than the top to minimize the problem mentioned by MJ.
Ok good to know. I already did buy the flat sawn. Should I also alternate the growth rings so the cupping direction is opposite every other board?
You can alternate the ups vs the downs as long as the pattern pleases you. On the tables I made for my children, you can see a difference in flatness if you look over the surface at glancing angle but not enough to have stuff roll over the edge. Pretty slight difference.
W/R to breadboard ends: Ughh, I made my daughter's drop leaf table with red oak and breadboard ends. The wood shrunk up enough that she has about 1/8" longer breadboard than table. And that is in NJ where you would think there would be high humidity. I will have to do razor saw surgery some time in the future.
W/R to 90 degree cuts, you could rotate the cuts kind of like I do on my jointer. I line up the assembly, mark one 'inside', the adjacent 'outside' where they position against the fence. On TS saw, up and down just make sure there is no tear out from the saw cut.
Enjoy the build! Tom
Have you considered breadboard ends? I believe the experts who say boards cup in the direction which is most exposed to moisture, not the natural direction of grain. For example, the boards on my deck all cupped upwards, no matter which side was up.
But I will suggest that you make sure your tablesaw blade is exactly 90º as I have had glued up boards that did not stay flat because the cuts were off by a degree or two.
Absolutely no reason to alternate growth rings. It won't do anything. A woodworking myth. Choose the arrangement that looks nicest.
Ok thanks John. I also heard to not join boards wider than 4”. Am I ok to just join the 3 boards for a 28” W? Instead of ripping the 9.5” boards in half
I much prefer wide boards. I would not consider a top with 4 inch boards. Not from a construction standpoint, but from aesthetics.
In days of yore, they used a single board for a top like that. I would too, if I could find a pretty one.
Welcome to ww'ing 101 you're going to learn a lot!
I totally agree with John on both the biscuits AND the growth rings. My feeling is if it going to cup there's not much you can to do stop it. Rings up/down or the same you'll either have a waveboard or a potato chip.
I just focus on a pleasing grain pattern the rings are what they are. NOTE: if you plan on hand planing the top grain direction has to factor into board arrangement.
Flat sawn lumber of ANY kind is THE most subject to cupping. White oak in particular can move a startling amount and is impossible to correct once its cupped.
You might consider bread board ends, although how much they prevent cupping is debatable.
With flat sawn lumber of paramount importance is storing the boards. ALWAYS keeping the lumber before and the top after glue up on stickers - Don't EVER lay the top on a bench even overnight you may be sorely dissappointed the next morning. No fans blowing over it either.
If you can, measure the MC if its over 10% if your shop isn't climate controlled I would move it inside your house for a few months.
The top is usually the first thing I do when building furniture. I usually "hold" them in cauls until I'm ready to fasten down.
I'm just the opposite. The top is last. I surface, rip and glue up all at once. Leave it in clamps overnight. Then cut to length, surface finish and attach it to the carcase. About 24 to 36 hours after being rough lumber.
Different approaches are fascinating.
Thanks all for your insight and wisdom. Last consideration-Wood using brackets like this on the wood seams help at all from restricting movement?
Any attempt to resist wood movement will ultimately fail. The wood WILL expand and contract with changes in moisture content, dictated by relative humidity. This translates as seasonal movement. The wood will expand across its width in times of high humidity (summer) and shrink at times of low humidity (winter).
An indoor conditioned space with air conditioning controlling humidity in the summer and adding humidity in the winter will reduce but not eliminate the movement. Embrace the movement in your design. Trying to stop it will result in cracking or buckling somewhere in your assembly.
Wow, you decided to build a countertop yourself? Why don't you want to buy a ready-made table? For example, I don't like to complicate things. I just recently ordered a table for myself on https://www.office-furniture.com.au/. For me, the main criterion was not to do it all by myself. I just had problems with the furniture all the time. I tried several times to assemble the countertop myself, and nothing came of it. Of course, there was an option to contact people who understand this topic, but why pay too much so I didn't suffer and just bought a table.
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