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Tolerance level for jointed thin stock?

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Forum topic by zombeerose posted 03-16-2010 11:04 PM 905 views 0 times favorited 6 replies Add to Favorites Watch
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zombeerose

79 posts in 3621 days


03-16-2010 11:04 PM

I have been designing a Greene & Greene influenced ceiling light fixture for my kitchen to replace the cheap ‘80s aluminum frame. For this project, I am trying to avoid making it bulky by using thinner stock (1/4”) in most places. However, I find myself getting rather frustrated because after jointing an edge then milling to the final dimensions, nearly every board stills up warping or bowing to some extent.

I am therefore curious how much tolerance I should allow for in each piece since the stock is thinner and can usually be straightened with minor pressure. In most cases, I am now considering joining two pieces together at right angles to help correct these deviations. Does anyone else suffer from these complications?

The wood is kiln dried walnut that has acclimated for years now.

-- Maximize - Your Time, Your Experiencies, Your Life, Yourself!


6 replies so far

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sras

4392 posts in 2595 days


#1 posted 03-16-2010 11:21 PM

Wood sometimes has stresses in it that result in shape changes when cut. It is a good idea to cut oversize, let the wood relax and then trim to final (& straight) size. Not sure if this will help…

-- Steve - Impatience is Expensive

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zombeerose

79 posts in 3621 days


#2 posted 03-16-2010 11:33 PM

Thanks for the response. I have been doing just that. Maybe this board is just doomed.

-- Maximize - Your Time, Your Experiencies, Your Life, Yourself!

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CaptainSkully

1437 posts in 3024 days


#3 posted 03-17-2010 02:36 AM

Yeah, there can be internal stresses that get released when cutting stock down to size to cause bowing. If needed, cut 1/8” oversize, then use a jointer to flatten/straighten the stock to final dimensions. Be careful not to flex the stock flat before jointing, as this will just let it spring back.

For G&G pieces, you might want to beef things up a bit to reduce the problem. The only parts I can envision 1/4” would be any kind of thin grill work, slats, mullions, etc. that are for decorative purposes. Of course the longer the piece, the more bow you’ll get out of it. Cross-pieces with half-lap joints might stabilite the bowing if that fits within your design schema.

Let us know how it works out. I’m very interested in designing/building an Arts & Crafts light fixture over our new dining room table when I eventually get around to it.

-- You can't control the wind, but you can trim your sails

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zombeerose

79 posts in 3621 days


#4 posted 03-17-2010 09:58 PM

Thanks for the info.

How long would you guys recommend letting the wood “relax?” Overnight, a week, a month…? I live in Phoenix and we usually have low humidity.

-- Maximize - Your Time, Your Experiencies, Your Life, Yourself!

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Michael Murphy

452 posts in 2471 days


#5 posted 03-17-2010 10:10 PM

It would help if you could orient the thin planks so that the growth rings are as perpendicular to the faces as possible. It would help keep them flat.

-- Michael Murphy, Woodland, CA.

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CaptainSkully

1437 posts in 3024 days


#6 posted 03-18-2010 05:00 PM

I’m pretty sure any spring will occur rapidly, so overnight should be more than enough.

-- You can't control the wind, but you can trim your sails

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