Working with casehardened lumber
Casehardened lumber should be returned to the processor, or planed to the desired thickness; resawing is not an option. 1998.
by Professor Gene Wengert
Q.
I am making a desk of cherry and am using hard maple for the drawer sides and backs. I have purchased 5/4 maple and am resawing it using my band saw before planing. On my first piece, I noticed that the two halves warped in opposite directions during the sawing and formed the equivalent of parenthesis like ( ). What is the reason for this? All I can think is that the outside is drier than the inside but it would seem, if this was true, that the warp would be like this ) (. I hope this isn't a silly question but I haven't done any resawing of hardwood previously and perhaps it is a common occurrence.
A.
You have a classic case of lumber with casehardening (actually "drying stress" is a better term as the case is not harder than the shell). The lumber was not properly dried and should be returned with a full refund, even the pieces that you have sawn. If you need a technical explanation of what has (or has not) happened, let me know.
If there is no hope of returning this lumber, you will have to use it full thickness, or plane it down to the required thickness, but plane each side a little at a time, alternating back and forth.
Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison.
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