Can a board flatten on its own?

[Dan McGonigle]

Hey guys, working on a hall table in cherry. The top is two boards edge glued, cut to width but still a couple inches longer than final length. The first time I placed the top on the base, it did not sit perfectly flat on the base. There was a gap, probably 1/16" or less, between the top and the base in the right front corner. No big deal, I figured once its screwed into place it'll close up, and even if there's the smallest gap, no one will know but me. Couple days later, the top is still where I left it on the base. This time the gap had closed up a bit and I was very pleased. Next I removed the top to fill a very small knot hole with dyed epoxy, so it was haphazardly positioned on cauls for a few days while the epoxy set up. I set the top back on the base tonight and the gap is huge, probably close to 1/8". Still counting on those screws to sink it down, but it is possible the top will relax a bit from its own weight and that gap will close? It was perfectly acceptable before, now its bothersome. Anyone have a similar experience?

[Ed Aumiller]

Depending on how the board is sawn will determine to a large degree how much it will warp / cup / etc...
Quarter sawn will have the least warp / cup... Flatsawn and riftsawn will have the most...
ALL wood moves with moisture changes.... If you allow for the changes, it should have minimum effect on the project..
Be sure to apply the same finish on both the inside and outside so the moisture change in the wood will be about equal on both sides of the boards...

Sometimes on flat/rift sawn wood it is better to rip it into more narrow widths to reduce warp/cup.. i.e. take a 9" board and rip it into 3 pieces and edge glue them back.. If you are careful and use a thin blade, the grain will line up excellent and it will reduce the warp/cup a LOT..

If you can, put it in the same environment it will be used in before fastening it place and just prior to finishing it...

[Paul F Franklin]

Ed provided a lot of good info. I will add a few thoughts. As Ed said, stock will move in response to changes in environment, particularly humidity. So when you bring stock into your work area you should allow time for it to acclimate to the new conditions. If the stock came from an unheated unconditioned storage area (like most lumberyards) and you bring it into a heated or cooled shop with much lower humidity, it can take weeks to acclimate and stop moving.

Machining the wood, especially resawing it or planing it to reduce thickness can release tensions in the wood and also exposes new faces to the outside, and the stock can (will) move again.

When I bring new stock into the shop, I normally sticker it (with weight on it) and let it acclimate for at least a week before doing any machining. Then I do rough machining, getting it flat and close to desired dimensions. Then I let it sit for a few days again. Then, ideally, I do final machining, joinery, and assembly in one session. Obviously, that is only possible on small projects.

The point is: the bigger the changes made to wood, via machining and/or change in environment, the more likely it is to move and the amount of movement will be greater.

[Andrew Hughes]

That’s Cherry for ya. I see what you did on the drawer fronts. :)

[Lee Schierer]

You can reduce the effects of moisture changes by finishing all sides of each piece equally. If the under side of the table top is finished the same amount as the top moisture changes will occur more slowly so there will be less effect. In the mean time insure that air movement and temperature are the same on both sides at all times.

[Jacob Reverb]

ALL wood moves

...alll the time and forever. The First Law of woodworking!

Second Law: Water always gets where it wants to go.

[Dan McGonigle]

These boards have been in my shop for probably 5 years. I just recently moved all my lumber out to my shed, but kept my current project lumber inside. It’s an attached garage shop, heated, but only when I’m working. Natural gas open combustion heater, so I’m not crazy about having it on when I’m not there. I’m sure those temperature swings aren’t good for my lumber, or tools for that matter, but that’s what I have to work with at the moment. I’ve never had a humidity problem, never any rust. The board were pretty flat when they were glued up. I’ve heard a lot about ripping from a wide board to joint and plane, the gluing back together. Never wanted to try it, risking having a slightly visible glue joint unnecessarily.

[Mike Cutler]

Don

As stated, wood moves. It may bow up and may bow down. Once you get it affixed inlace the top should equalize stress as it's allowed to move.

I've never ripped a wide board, just for the sake of ripping it. I know folks do it, but I don't. I also won't use flat sawn material for large panel glue ups.

[Brian Holcombe]

Same as Andrew I’ve had the most unexpected movements from cherry. See if it pulls down, if it does then it will probably be fine.

Cherry seems to require every imaginable preparation be made for wood movement such as bowing and cupping (in addition to normal shrinking and swelling). I built a cherry cabinet a few years ago and had to make many accommodations on it that I did not on the identical walnut cabinet.

Anymore I try to mill well in advance to a project and for wide or long boards I will mill in stages with a few days in between. That way I can gauge how the wood behaves as stresses are being exposed. I like to do final milling then cut joinery straight away. I don’t like to give it time to sit around and think about how to misbehave.

Woodworking is a constant learning experience, which is both wonderful and aggravating. It’s not that predictable and it likes to remind you of that occasionally. As example I had a board of Iroko which twisted into a corkscrew as I resawed it, tried to save it but ultimately it became expensive waste. I sawed another of the same, bought at the same time from the same place, sawed dead flat and stayed that way.

[Dan McGonigle]

I guess I should have known. I try to plan for movement. Always do my milling over several days. I’m relatively new to woodworking and have only worked with a few species and cherry has certainly been the most difficult, albeit one of my favorites. I agree that quartersawn would have been preferable for the top. I bought a large piece of riftsawn 8/4 for the legs, but other than that everything else is made from the same tree, so it’s important to me to keep that same color throughout. I bought this cherry in bulk probably 7 or 8 years ago from an amateur sawyer. It wasn’t cut, dried, or stored well. But it was dirt cheap and the grains been pretty nice. Thanks guys

[andy bessette]

...I bought this cherry in bulk probably 7 or 8 years ago from an amateur sawyer. It wasn’t cut, dried, or stored well. But it was dirt cheap...

You have learned a valuable lesson.

[Bill Dufour]

What is the climate like in your shop and part of the world? Does the humidity change much or is it stable year round. It would help if we knew where you lived. All I know is you heat your shop, year round or only in winter? Burning any unvented fire in the shop is going to cause moisture issues. I am surprised you can still buy unvented heaters in parts of the USA and I guess in your country as well.
Burning a pound of propane or NG will release one pound of water into the shop.
Bill D

[Dan McGonigle]

New Jersey, about 20 minutes from Philadelphia. Heats only on when I’m working, couple hours 3-5 nights a week. The NG heater is vented with an exhaust fan to the outdoors. What I mean by open combustion is that the combustion chamber is open to the atmosphere, allowing dust and such to enter and burn. It sucks in unfiltered atmospheric air, that being said, that flame is also open to the atmosphere. That’s why I don’t like running it unoccupied. It’s a Modine unit. So this time of year, it’s very cold in the shop, close to outside temp, usually a little higher. If it’s 30 degrees outside, I can be working at 65 degrees in 25 or 30 minutes. Great for me, not so great for lumber and tools I suppose.

[Michael Stockdale]

If you're extremely lucky... then, yes... a board can flatten itself. I suggest purchasing lottery tickets very soon... before said luck runs out! :)

Michael

[Steve Schoene]

I have a reproduction card table that in winter has the top leaf that lays exactly on the lower leaf. In summer one corner lifts about 3/16th inch. Interesting enough, the original I copied from also has a leaf that is similarly lifted on one corner. The original, in the Metropolitan museum of art, is pictured in Figure 2.7 in Michael Moses, Master Craftsmen of Newport. I'd bet that the John Townsend Original would still sell for a pretty penny, should the Met de-accession it for some crazy reason.

My guess is that day to day changes in moisture levels are affecting the top. I would be confident that when screwed (with fasteners that allow the width to change) it will be fine. I wouldn't rip and reglue. Besides making it narrower, with the risk of a glue line, it can still move. Properly screwed such small lifts won't be a problem. You wouldn't be able to stop the width from changing, short of crushing the wood, the width shrink or swell is a more powerful force.

[andy bessette]

...risk of a glue line...

What's the big deal about a glue line?

[Steve Schoene]

I avoid glue lines. Do do so takes a lot of work.

If you can see one, other than at the place where grain changes a bit between boards, you are producing sloppy work. Often that’s ok depending on the use of the object but not always.

[Leo Graywacz]

Finish both sides equally. Screw it down. As long as it doesn't warp the leg system don't worry about it.

[Dan McGonigle]

What's the big deal about a glue line?

Glue lines are inevitable and impossible to avoid, usually. I’d like to make the glue line as unnoticeable as possible though. For me, a glued panel should look cohesive, rather than obvious and abrupt changes in grain direction or color. Just personal preference I guess. I’d like to look at the top of this table and see a 15.25 by 48.5 top, instead of two 8 inch boards glued together.

[andy bessette]

Ripping a board and gluing it right back together should not produce a noticeable glue line as the grain pattern is virtually uninterrupted.

[Jacob Reverb]

To me, glue lines should either be a) almost impossible to find, or b) obvious.

As in most design elements, contrast is fine, and invisibility is fine, but where you run into trouble is all the grey area in-between – particularly where it appears the builder tried to "hide" something, because "hiding" suggests "mistake."

One design element that calls attention to itself is putting a kerf on the edge of a board where it butt-joints another board at 90°. Somehow, the joint looks crappy without the kerf, but with the kerf, it throws a shadow that says, "Yeah, I'm just a lowly butt joint, and that's all that I'll ever be" – but it just looks "right."

In a way, it's analogous to color: Matching colors are fine, complementary colors are fine, and contrasting colors are fine – the trouble lies in where it appears someone tried to "match" colors and failed miserably.

In my opinion, most beginners are better served by either calling attention to, or at least ignoring, the inevitable discontinuities in woodworking rather than by trying to "hide" them. I call it the "Plastic Wood Corollary." I'd much rather see a sunken nail head than that miserable material, ever, anywhere, except under paint.


I’d like to look at the top of this table and see a 15.25 by 48.5 top, instead of two 8 inch boards glued together.

But...that's what it is, isn't it? If you wanted no discontinuities or imperfections, why didn't you go with Formica or plastic or metal? Just kidding...but you see what I'm getting at. Sometimes you just don't have enough material to find a way to arrange the boards such that you can make ALL of the glue joints invisible. In such cases, I'd rather see ALL the glue joints be obvious, rather than just ONE, again, because ONE mismatched glue joint is more of a discontinuity – and looks like more of a "mistake" – than ALL of the glue joints being mismatched. When they are ALL mismatched, it tells the viewer "the glue joints don't matter." Which they don't.

[Ron Citerone]

It's nice if you can find wide boards to glue up a side or top from one board, or boards cut from the same log, but it isn't always available at reasonable prices. I made a piece from walnut that came from some wide boards from the same log and depending on the light and the direction you are looking, some parts have a different darkness or lightness and contrast. I'll still take unstained lumber with a clear finish over stained every time.

Managing pieces for equal moisture exposure is a constant battle while in the building process. I either sticker after processing, or if I stack up some panels on a table, I put an impervious surface on top followed by something for weight. When I was a beginner I underestimated the importance of bringing wood inside to acclimate as well as managing storing project pieces from initial planing to glue up and finishing. (Often with unpleasant results!) Live nd learn......that's the interesting part of it all!

[Steve Schoene]

Glue lines are not inevitable and, with solid technique, can almost always be avoidable. Just running the boards for several passes over the jointer is seldom enough. After the initial edge straightening and laying out the boards for the most desirable grain patterns, clamp one board vertically, with the edge to be glued, on the bench. Then lay the next board on that. In a darkened room, shine a light behind the two boards. You will almost always see some light between the boards. Mark any places with chalk any places where the boards touch. Then, with the jointer set for a fairly light cut and with a carefully squared fence, lower the boards onto the jointer to make a short cut in the area around the marked touch point. (You are likely to notice a minor grain anomaly in that area.) Then make full passes with the same jointer setting. Retest for a light tight joint between the two boards, when held together witha light hand pressure. When you can pass that light tight test for all boards you are ready for the glue up. Put glue on both edges and clamp with really firm pressure.

[lowell holmes]

I would do what I have done successfully, rip the board down the middle and glue the halves back together with the bows opposite each other. The seam will be acceptable.

[Stan Calow]

I know some would consider it cheating, and may not work with your design, but I've used 1/4" birch quarter-round to cover gaps like that. I've also added thin wedges of wood on top the apron to fill the gap, but thats a lot more work.

[Jacob Reverb]

Hmmm...it appears that we are talking about two different issues here.

When I saw the term "glue line," I thought someone was talking about the grain/figure not "matching" between adjacent pieces in a glueup.

I now realize some people are actually talking about GLUE lines ... where you can actually see a layer of glue between boards. I've only seen glue lines once, on a bar top that my landlord had glued up, apparently without any clamps. I agree that looks terrible and screams sloppy (and usually structurally unsound) work.

IMO, the former issue isn't an issue, but the latter issue is unacceptable...