Sawing Elm with Off-Center Pith

      Off-center pith in a leaning tree is a sure sign of stressed wood, and the logs must be sawed with special care. May 11, 2005

Question
Just dragged a 30" (large for Manitoba) American elm out of the woods. A victim of Dutch elm disease. Although the bark comes off quite easily, the wood seams solid. The tree was leaning only slightly, but the pith is quite off centre. What implications does this have for sawing technique or the quality of the lumber? I want to cut 5/4 with a bandsaw mill.

Forum Responses
(Sawing and Drying Forum)
From contributor E:
There is a lot of stress built up in the tree you mentioned from the position the tree grew in. As a lumber grader, I was taught that it causes a severe degrade of lumber. But if you cut it properly, you can minimize the loss. It's taken me several years to find the proper ways and every log is different. Try to find a sawyer locally that is willing to give you some help it's easier to show someone than to try to tell them.



From Professor Gene Wengert, forum technical advisor:
Off-center pith in softwoods is an excellent indicator of stress within the tree and compression wood. In hardwoods, you can have stress with or without the pith being off-center. Yet the off-center pith is unusual, so you can expect unusual wood... stress is more likely along with tensionwood. Flat lumber (after drying especially) will be a problem most of the time.


From contributor M:
When sawing off-centred logs, you have to keep the big side completely parallel to the smaller side and saw threw x threw. If tension and compression wood are included on the same board (not following my directions, i.e., cutting askew), the board will twist. If you cut at 90 degrees from my directions, the board will bow and probably split part of the way down the middle.


From the original questioner:
Thanks for your responses, but I need some clarification. Does this mean that on a horizontal bandmill, I would for example turn the log so that the big side would be on top and the small side at the bottom and then cut through and through? I'm assuming it would be advisable to turn the log 180 degrees after a few cuts.


From contributor M:
Yes, you would need to turn the log 180 degrees. What I said is not necessarily true, because I have cut some large oak branches that were leaning sharply and with a lot of twist making the two sides wrap around, and was surprised to get very little bow or twist in the boards. Those branches yielded some nice curly white oak.


From contributor B:
For what it's worth, my experience with elm is that it is a highly tensioned wood under the best of circumstances.


From contributor M:
I like to use elm for those furniture parts that are used to reinforce joints, etc. because elm does not split easily. These parts are usually small, so it does not matter if the boards they are made from warped in the drying process, except that straightening a warped board before cutting takes more time.

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