Dealing with crooked logs

      What is the best way to saw logs with sweep or crook? May 30, 2001

What is the best way to saw logs with sweep or crook? If I were to use the boards myself, I would cut the log into short lengths, if I could then saw parallel to the bark. Or I could lay the log on the flat side and saw through and through. Of course, I could saw from the longest, straightest end and use the rest for firewood.

I read about a curve saw that can saw parallel to the bark on curved logs. The boards are then straightened in the dryer. And I thought warp came from drying!

Forum Responses
Except for cup, warp is not related to drying, significantly. (Bow can be related to how well the lumber is stacked, but stacking is not "drying.")

The best (highest grade and volume) way to saw a crooked log (if you can do it safely), is to position the log so that the ears are facing the saw. Then, saw the ears off in one cut, getting a flat surface along the entire log length. At the narrowest spot, this surface should be about 4-1/2 inches wide. You may have to cut the ears in several passes to avoid large hunks of wood. Unless there is a lot of sweep, you cannot normally get any lumber from the ears. Note that this step does in one pass what the edger will do in several passes.

Next, rotate 180 and cut off the belly of the sweep. In this step you can produce shorter pieces of lumber. Continue until you have a flat surface full length. At this point, all the sweep will be removed. Now, proceed as you normally would, sawing a log. However, note the next paragraph.

Lumber from the first two sawn faces (ears and belly) will have a tendency to side bend. Therefore, we minimize cutting on these faces. The lumber sawn from the two un-sawn faces will have a slight tendency to bow, but such bow will not be a quality problem.

It is a poor choice to put the sweep at 45 degrees to the saw, as then you will get side bend in almost every piece of lumber during drying. Plus, yields will be lower.

Gene Wengert, forum technical advisor

From the original questioner:
I assume you meant 90 degrees to the blade, not 45 degrees.

I understand the reason for sawing the ears on top is because of tension-compression wood in the log. But wouldn't a disadvantage be the cross or short grain boards produced?

I meant 45 degrees, which is sometimes done. This means that every face will have some effect of the bow. Obviously, this is not a good idea!

Also, putting the sweep 90 degrees to the blade is okay, except that every piece will require substantial edging. Also, holding the log in this position can be a problem (safety issue) on many mills. So, work on the other two faces first (belly and ears), getting good bearing surfaces and essentially edging the lumber from the other two faces on the carriage before it is even sawn.

Gene Wengert, forum technical advisor

Cut the points off... first cuts. This cut parallels the final board's wide surfaces.

Turn 90 degrees, cut the flitch off (this is the board edge cut). Turn 90 degrees, cut the flitch off. This is the first cut that will start making boards.

The original bow of the log will create a bow or stress in the lumber, which can easily be nailed out of the lumber as opposed to having a 2x6x10 with excessive crown when used on edge.

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