Sawing to Prevent Tapered Logs
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Making the proper cuts in the right order, to produce flat, quality lumber. May 11, 2005
Question
I have been sawing some 20' poplar logs (the boards sure do bow). When I raise the toe board to level the log for my first cut, make a good long flat cut, then flip the log and have the cut side down laying on the mill, the next cut I get is a slab that's really thin on one end and really thick on the other end. Wouldn't this be the same as if I just cut the log without leveling it with my toe board, except my first cut would have the big thick and thin slab and my second would be pretty much uniform?
Forum Responses
(Sawing and Drying Forum)
From contributor S:
Are you making the top of the log level using your toe board? I think what you want to do is level the center of the log using the toe board. This centers the heart in your cant when you flip the log.
From Gene Wengert, forum technical advisor:
Indeed, you are correct about having one face or the other parallel to the bark and the other containing the taper. For this reason, we put the taper into the poorer face and saw the best face parallel to the bark. For really high quality logs, we would actually saw both faces parallel and then when we get to the low grade part of the log, take the taper out and throw away a low grade tapered piece of lumber. This is SOP.
From contributor B:
The method Gene describes is absolutely the best way to get the highest quality lumber, but in the real world, average Joe Homeowner customer likes his board with parallel edges, so the method contributor S describes is what most portable sawyers I know use, essentially splitting the difference in the taper between the two sides.
From contributor G:
I take it you are sawing on a portable bandsaw. If you are mobile, then your frame is probably flexing. I gave up moving my mill and made it stationary, on concrete, and perfectly level. It is very hard to level them up in the field and keep them level. If one end of the log isn't springing up due to stress, then the frame is moving, and they can move a lot when they are not on something solid. Remember that the sawhead rides on a rail or rails, and they will flex and move if not properly supported. Your first cut is probably not flat, although it appears to be. I had this problem with my Wood-Mizer on logs that were over 12 foot. Thick and thin.
From Gene Wengert, forum technical advisor:
If you saw parallel to the bark, you will have flatter lumber after drying, higher grade lumber, and less edging to do. Split taper sawing actually gives the worst results in terms of value and warp. The difference in value is about 20% when not sawing a medium grade log parallel to the bark.
From contributor B:
Gene, I wish we had emoticons here so I can emphasize that I am not arguing, only asking so I can improve my skills. In a large commercial operation with edgers and resaws, I can see how full taper sawing can easily work. How about us portable guys? Let's say I have a tapered log on the bed. My first cut on each face is parallel to the bed, then 1 or 2 flitches are taken and put in the cradle for edging later. I now have a tapered cant and want to continue sawing for grade. I have to either level the cant up with the bed again, a time consuming effort, or saw from the bottom, then turn the cant to remove the board and see what the new face reveals. Both these options are chewing up my client's money, since I bill by the hour. Is there another method I am missing?
As I mentioned earlier, while I am well aware grading rules allow tapered width, most clients want parallel edges cause that's the way Norm's are on PBS, so my edging time is now increased.
From Gene Wengert, forum technical advisor:
First, put the best face down on the bed. This assumes the bed is parallel to the saw. Now, saw the opposite face, which is probably not a good face. You will take the taper out of this poor face. When you rotate 180, you will now be parallel to the bark. Note that the cant is uniform thickness, so no tapered lumber is produced.
Should this opposite face be a good face (clear) and also the log is over 15" so that clear lumber will be underneath, you can taper the log onto the bed to saw face #1 parallel, and then when you rotate 180, you will also have to use the taper to saw the best face parallel to the bark. The cant is tapered, but the value increase of 20% certainly pays for tapering, even on an "Armstrong" powered mill. You then remove the taper sets and saw the log once to get rid of the taper in the cant, after the high grade is removed. Then go to the other two faces.
Note that you will have less edging and the customer will have flatter lumber after drying = more useful. Also, you will not have to edge short pieces... a real pain. This is for small mills.
