Shrinkage allowances for red oak

      Estimating radial and tangential shrinkage when drying red oak to 12 to 14 percent MC. 1998.

by Professor Gene Wengert

I am going to slice 6/4 green northern red-oak (quercus rubra) to make flooring wear layers for a Swedish laminated flooring company to a thickness of .189" x 8-3/4" in width, and then dry these wear layers to 12-14% or so.

My question is, with a rather gentle forced-air kiln at a temperature of approx 95 degrees F, how much shrinkage should I allow for radially and tangentialy as well?

Also, as we are in Idaho, we use a lot of white spruce stickers. This should hopefully not stain the wood. Would spruce be the desired sticker-material?

The standard shrinkage values for northern red oak from green to 12% are averages (so half the pieces will shrink slightly more) and also vary for each species of red oak. To be 100% safe, I would expect 9% tangential and 4.5% radial. This means that all pieces will actually be too wide, so you may wish to save a little wood and make them 4% and 7.5% larger, which means that once in a while you will have a narrow piece, but not very often.

No problem with the spruce sticks if they are dry.

Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison.

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