specific question
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Bill Tindall, E.Tn.
The radial and tangential shrinkage of norther red oak is 4 and 8.6% respectively, going wet to dry. A 48" oak disk will therefore shrink 1.9" in diameter and 13" in circumference upon drying. (in practice these numbers will be less for the oak may not dry this much in its final environment). You found that a 1" hole cut out of the center would relieve this differential stress from drying? 3" hole from rot with accompanying degradation of the adjacent wood is easier to understand.

To get zero stress upon drying the diameter must shrink the same percentage as the circumference. Putting a hole in the middle provides a place for the diameter to shrink more if the hole is big enough. The strength of the wood will provide some resistance to splitting even if under stress. Oak is exceptional for its lack of splitting strength when stress is perpendicular to the rays which will be the case for drying a disk.

No doubt someone will provide pictures of successful tables made from disks.

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