Euro oak

[marcros]

How much can I expect kiln dried euro oak to expand and contract when inside a centrally heated house due to seasonal movement? (Ideally as a. % Of the width) It was at 11% moisture when I bought it Friday using my cheap metre, but I can't find any figures to work out the length of breadboard ends etc on a table top.

How risky would it be to use it pretty much immediately for things like table rails and legs? It is 1 1/4" sawn if that makes any difference to make a table with. The top will be 4 boards, breadboard ends (only pegged in middle) and fixed to the base allowing for movement. Rails are 4" fixed to legs with a draw bored mortise and tenon.

Cheers
Mark

 

[carlb40]

Not sure if this applies to furniture? But Chris schwarz mentions in his bench book about using wetter timber on the legs. Because when they dry out the joints ( draw bored ) become stronger. So would think it may apply here as well?

 

[Phil Pascoe]

I'd have thought "wetter" wood on the legs would do the opposite - the dowel pulls the tenon against the leg, if the leg then shrinks.....?

 

[kostello]

http://www.woodworkerssource.com/movement.php


Hope this helps

 

[marcros]

http://www.woodworkerssource.com/movement.php


Hope this helps

Cheers. It suggests that on American White Oak there shouldnt be much movement between a moisture content of 15% and 8%, so I am not that concerned.

Quite a useful site that one, thanks

 

[marcros]

I'd have thought "wetter" wood on the legs would do the opposite - the dowel pulls the tenon against the leg, if the leg then shrinks.....?

I think, and it is some time since I read the book, that his idea/point was that it puts the dowel under greater bending stress, and so tightens the joint that way. I think that he was also only talking about "wetter" being a % or so higher in moisture rather than anything more. IIRC, it was having bought a number of lengths from Home Depot at the same time, getting them home and sorting through them- so the MC is going to be pretty similar. If used on the top, the "wetter" wood would risk going out of flat as it dried, so it was a matter of using it on rails or legs. That was my memory and onterpretation anyway.

 

[Steve Maskery]

I don't buy the wetter legs argument either. Not in that context, anyway. In a Windsor chair, yes, because the hole will shrink and tighten around the tenon, but that is a very different scenario.
Your BB ends will often be a bit longer or shorter than the width of your table. It means they are working properly!. I don't think you have a lot to worry about, to be honest.
S

 

[custard]

Simple answer, 11% moisture content timber is fine for internal applications.

Slightly more complex answer, you'll experience some movement whenever you cut wood..even with appropriately dry timber. I've just deep sawn some straight grained, quarter sawn, sapele boards that were at 10% moisture content and in equilibrium with the prevailing humidity of my workshop...overnight they bowed slightly, about 1.5mm on a 900mm length. This was due to internal stresses being released. So if you're really fussy then cut down to final dimensions in several stages, giving the workpiece a few days to acclimatise at each stage.

 

[Sgian Dubh]

How much can I expect kiln dried euro oak to expand and contract when inside a centrally heated house due to seasonal movement? (Ideally as a. % Of the width). Mark

Use a factor of 0.3% for each 1% MC change if you're calculating the change in width of tangentially sawn European oak. [Later in this paragraph note that calculations that include 0.3% as a factor are expressed in the form 0.003, ie, the decimal point is moved two places left.] For example, if you start with a panel 900 mm wide at 7% MC and it absorbs moisture to become 13% MC do the sum 13% - 7% = 6%. Then 6(%) * 0.003 = 0.018. Then 900 mm * 0.018 = 16.2 mm (growth in width). Add the 16.2 mm to the original 900 mm to get 916.2 mm, the new width at 13% MC as opposed to the original width at 7% MC.

If you're working with radially sawn European oak use the factor 0.18%. Then do similar calculations as described above.

Also bear in mind that although there are several good sources for expansion and contraction factors for a vast range of woods between FSP and oven dry, it's my experience that all the results of calculations tend to overestimate the actual change in width. One reason for this is that expansion and contraction across the range of MC that wood shrinks or expands, ie, 30% MC down to 0% MC, the shrinkage or expansion factor for each percentage change in MC is not linear; the greatest proportion of shrinkage (and distortion for that matter) tends to occur between about 20% MC and 5% MC.

Other factors play a part too, eg polish slows down the adsorption and desorption of moisture in wood. And then there's a hysteresis loop wherein wood that is returning to a higher moisture content from a lower moisture content won't reach the size it was when it first dried down to that that higher moisture content from a yet higher one. Slainte.

 

[marcros]

thank you everybody.