Thread: Wood movement

Such as a dresser with panelled doors that I had to plane off as soon as winter came. The biggest problems come if you don't fix them immediately and then some heavy-handed person is sure to come along and damage the hinges or worse.

I suppose we've got it fairly easy down south (vic) unless, and it's a big unless, you have air-conditioning in the house. Then you can expect some changes in moving an item from the shop. I gather it's easy to damage antique furniture in such conditions unless you keep the moisture level up.

So, sealing the timber won't prevent movement so that the spaces between the drawers will remain presentable? Even using a tung oil/poly mix? What about a sanding sealer first? Is it actually possible to truly seal timber? Do the lids on your fine boxes behave?

I like mixing timbers and I believe there are charts available showing tangential movement of various timbers at varying humidities so, does one have to refer to these charts (where available) and then use species that are similar in their movement characteristics? Jarrah and huon pine, on first guess, would be unlikely to have similar behaviours.

Hope the Brisbane owner of your jewellery chest doesn't decide to move to Tassie or Darwin, for that matter.

FWW published a table a few years back (article by Jugo Illic) showing radial and tangential expansion of a large range of timbers. Generally, lengthwise expansion is negligible. I have it on my workshop wall for reference & will post the issue No. when I go back down there.
The problem comes when you have something like drawer fronts with the grain running across, contained inside a compartment with the grain running vertically. An increase in ambient RH will cause the drawer fronts to expand vertically (& from back to front, but that doesn't matter) and they will jam against each other.
The problem doesn't usually arise with boxes as long as you leave the lid and bottom panels floating, so that they can expand and contract within the sides or lid frame. The exception is with a book box like this
Book box 1.JPG, where the grain is running vertically on the sides, front and back (no problems there) and transversely on the top & bottom. This is usually not a problem, as the conflict occurs between the narrowest sides.
The difference between jarrah & huon pine expansion in similar directions is not too much. With most timbers, providing the expansion in both pieces is across the grain (radial or tangential) there won't be a problem. The only time I've had a problem is with casuarina, which seems to move a lot more than most other timbers.

PS. I don't believe it's possible to completely seal a timber against moisture transfer (and maybe you don't really want to) unless maybe one of the pour-on finishes works. However, I think most finishes will attenuate the moisture changes, particularly oil & wax. For this reason, it's important to use the same treatment on both sides.

maybe this will assist:

Estimate Wood Movement Calculator

Cheers

Doug

Originally Posted by Dovetail

So, sealing the timber won't prevent movement so that the spaces between the drawers will remain presentable? Even using a tung oil/poly mix? What about a sanding sealer first? Is it actually possible to truly seal timber?

In a word, NO!

Well, not practically - a thick coat of epoxy resin does a fairly good job, but you are hardly going to finish a fancy jewellery chest that way. Many years ago FWW also ran an article on different finishes and how much they slow down moisture ingress/egress. The difference any finish made was surprisingly small, and oil finishes of any type made the smallest differences of all.

Wood movement is just something to accept as inevitable, like death & taxes. As Jim says, it's not too bad when you build for you own local conditions, you eventually learn to strike a happy medium between drawers that move at any time of the year and gaps you can tolerate in the driest months. Building drawers with zero clearance is just asking for trouble, and wood always obliges. And you also learn to avoid some woods like the plague! Airconditioning/heating, and our predilection for upping stakes & moving to different climates adds other dimensions (literally!).

Cupping after resawing is usually due to moisture gradients in the wood, so more likely to happen during periods when it's drying out after prolonged wet weather or vice versa. If the wood was well-dried in the first place, & doesn't have any nasty internal stresses caused by poor drying regimes, it should settle once things even out, but of course that doesn't always happen, particularly with our Eucalypts and their every-which-way grain. For critical bits like drawer sides, I either plane down evenly from both sides, or resaw a little oversize, let them rest a while, then do the final dimensioning.

You can avoid many problems by being familiar with your woods and by careful selection for grain orientation, avoiding sapwood & wild grain in anything you want to remain flat & true, etc., but no mater how much care & theory I apply, I still run into ornery pieces that do the 'wrong' thing and twist or cup just to spite me. In these cases, there's no point in doing other than what Alex did - start over!

Cheers,

For critical bits like drawer sides, I either plane down evenly from both sides, or resaw a little oversize, let them rest a while, then do the final dimensioning.

This is pretty well essential for drawer sides. Also, there are a few woods that are very stable and good for drawer sides - WRC, larch, kauri are usually good.

It's a price we pay for working with an organic, breathing medium. The satisfaction and final results far outweigh the labour and worry put into it.

What about investing in a humidifier. Temporarily raise the humidity in your shop until the job is done.
I believe that a lot of luthiers use them, especially in country areas.
Eg Beurer LB44 Air Humidifier - Air Treatment | Harvey Norman Australia

Yes, I think that would work. Not sure what its duty cycle would have to be.

There is a larger model available as well as other brand alternatives.
Beurer LW110 Air Washer and Humidifier - Air Treatment | Harvey Norman Australia

I've used a similar thing before when my son was sick when very young. You fill it up with water once a day.
In the US I believe you can get models where you can dial in the desired room humidity percentage up to about 50%.

I'm sure the humidifiers would work in an enclosed workshop. However, I work in a garage with the roller door open, so maintaining a higher humidity isn't going to be possible.
Guess I'll just have to make allowances and hope all goes well. I can always arrange for someone in Brisbane to plane a bit off the bottoms of the drawer fronts if necessary,

Does anyone here use those wood moisture meter thingies? On the few frame and panel pieces I've made with wideish panels, I've guessed an allowance for panel wood movement depending on whether I was constructing during winter or summer. I appear to have always been over generous and while the panel shrinks and moves unequally in the frame it eventually ends up hard against one stile and showing a gap on the other side.

I've read about using tangential shrinkage tables and a moisture meter to work out where in the cycle you are to make a better calculation for movement allowance. However I've taken apart some sound old solid blackwood machine made kitchen cupboard doors that appear to have effectively zero movement allowance. How do others work out panel allowances and how deep do you go on grooves in the stiles?

Originally Posted by Fuzzie

Does anyone here use those wood moisture meter thingies?

Nope, but I've often thought about getting one. I wouldn't use it for stuff I'm working with on a daily basis, but for following the progress of wood drying from green. However, inertia, and the fact that I never get around to using anything I've cut until long after it's likely to be well & truly equilibrated, keep a moisture meter well down the priority list.

Of course, equilibrium is affected by storage conditions as well as prevailing weather patterns, so it would be nice to know exactly whayt you are dealing with when fitting critical parts like panels. However, you can make a few guestimates & get close enough for the purpose, I think. I don't use tables, myself - been at it enough years now to know that for any woods I'm likely to build doors from, 13mm (1/2") deep grooves are adequate for most door panels up to around 350-400mm wide. If I'm working at the most humid time of year, I fit the panel fairly tightly, and if it's bone dry (as it is here atm!), leave up to 5mm each side. Haven't had any problems with visible gaps or split panels for a very long time, now...

I've certainly had the unpleasant experience of a gap showing on one side of a panel a couple of times, and a split panel on at least one occasion. It can happen if glue seeps into the groove & catches one side of a barely adequate panel & so all the expansion & contraction appears at one side, or in the latter case, it was excess glue seeping into the groove & locking the panel. Apart from being more careful about applying glue to the frame joints, I now pre-finish all panels, & wax the corners before glue-up, to avoid these problems. Some people routinely use a small dowel top & bottom (at the back of the door), to keep panels centred, & make sure expansion & contraction are even on both sides. I've done that on a couple of occasions, but I don't think it's necessary unless you are worried about your panel being a bit narrower than it should be.

In general, frame & panel construction is a pretty robust & reliable method, & it's been successfully accomplished without the benefit of moisture meters for a very long time. Experience will be your guide, & if you follow a few simple routines, like making your panels early in the job & giving them a week or two to settle before final sizing, it should minimise unpleasant surprises.

Cheers,