Learning how to deal with stress

[YellowHammer]

As you are sawing, and if you look closely, you will see the boards react during the cut in different ways.  Some will lift off the cant like a carrot peel, those will have stress in the face plane and will not dry flat, but will dry straight along the edge plane, such as needed for dimensional lumber where all the edges of the boards need to be straight to not have a floor that looks like the waves on the ocean.

If during sawing, the boards lay flat but flex sideways, as shown on the OP picture, those boards have stress in the edge or shear plane direction, and will dry flat on their faces which is optimal for high grade furniture wood.  Looking at the picture, you can see that the boards have
a considerable amount of stress as their edges have flexed sideways a pretty long way, like stair steps, but are still laying dead flat.  It is a great example of identifying stress when sawing, and then putting that stress on one pane only to make very flat wood.   

Some techniques intentionally force the stress in one plane such as when quarter sawing.

The worst stress orientation is a board that is sawn where the stress is not oriented in one plane only, which causes twist and makes the board bad for both dimensional and furniture lumber.  Basically, the worst of both worlds and sometimes called a boat or airplane propeller. 

Identifying lumber stress real time when sawing, and then being able to manipulate that stress to the desired plane is one of the most important skills a Sawyer can learn in my opinion.

It's not really that hard to identify stress, but it is a subtle thing, and people may saw for decades and never notice the signs, then the lightbulb goes off and they can never "not see it." It's one of the things I harp on in my videos, because it is so important.

[Digger Don]

Would it be safe to say that if the log looks like a ")" as it sits on the mill, that's how the lumber will look if you saw from the top down? For the purpose of this question, I'm not turning the log at all, just sawing from top to bottom.

If I'm understanding MM, by sawing the horn or the hump, the boards will be much easier to straighten when used. The boards will rise up, rather than sliding sideways, as in the OP. Correct?

[kkcomp]

I ask that everyone pardon my ignorance, but how do you know the log has stress in it?

I see no ignorance in your very legitimate question.  We all have fairly different markets so we handle the stress to better accommodate our customer's cut list whether that customer is ourselves or another person.

Mine is certainly different from virtually everyone else because 90%+ of my sawing is SYP for framing lumber.  That being said, I can accept bow but not crook, so I almost always saw through from either the hump or horn faces of a log.  Yes, some logs have sweep on more than one face, so I look, turn, saw, and move one to the next log. Opening Face LINK

Magicman, I have a lot of SYP and access to much more I would like to make dimensional out of. How do you deal with all the sap? I have stopped cutting it because it just mucks the blade up too fast and makes waves.

[Magicman]

I see that you are in Jacksonville and are probably sawing more Slash and Longleaf than I do.  Mine is mostly Shortleaf with some Loblolly.  I still use 2 oz of original (light green jug) liquid  Cascade per gallon of water and have very little problem.

Longleaf sap is sticky, runny, and miserable to deal with.  Of the few times that I have sawed it, I had to squirt the blade with Diesel after each pass.  Longleaf logs are much better to deal with after they have been felled for about 6 months and the logs have aged, bark slipped, and the sap hardened.  Even then some individual LL logs are miserable to deal with.  I actually prefer to saw all SYP logs after they have aged for a few months.

@caveman saws a good bit of Longleaf and I believe that he has converted his LubeMizer over to Diesel.

[caveman]

Slash and Longleaf do seem to saw better after sitting for a month or so (about when the bark begins to slip).  The slash pine we have been buying lately is the sappiest we've ever sawn.  We are planning to cobble up a "lubemizer" type apparatus using pumps and solenoids.  The gravity fed blade lube and the spray bottle have not been cutting it lately with this slash pine and the live oak we've been sawing.  I'm spending way too much time cleaning blades prior to sharpening.  

Somebody, send me some rain.  

[TimW]

I am sending all the rain we have, but Magic Man is between here and you.  He may have to relay it for me.
I love sawing Loblolly when the bark starts falling off.

[Machinebuilder]

Thanks to Roberts video's, and trail and a lot of errors



This log had a considerable bow to it, a couple inches of taper and more knots than I thought.
My opening face was like Magicman and took the horns off. I then squared up to a cant and when I started cutting boards I saw a bow.
So I rolled it 90 and got this result, a very visible side shift. what was really interesting when i got to the last cut the board shifted the opposite direction.

Thanks to People here I am getting better, Maybe I'm making less designer firewood.

[Digger Don]

Well, that's a lesson learned. When typing a quick reply, don't go back to a previous page. All gone.

I was wondering if there is a way to identify the stress before putting it on the mill. (See post # 26.) Assuming (I know, I shouldn't do that) that the log is not turned at all, just sawed from top to bottom, is it correct that the lumber will take the same curve the log had?

YH: Is Chip back to his full time supervision role, yet?

[barbender]

 In my experience, any grain you saw through that is not parallel to the cut, will move. For a couple of examples of what I mean, if I have logs that have a large root flare that I saw through, the boards will follow the shape of that flare because the grain turns and follows the shape of the outside of the tree. Same thing with a bowed log, when you saw straight through it you are cutting across the grain and the board will follow that shape.

 Some large mills have "curve saws" that saw through curved logs basically parallel to the bark. I've never watched one, but guys that have told me the lumber comes out of them laying flat.

[barbender]

 This is a good animation of how a curve sawing line works-

 https://youtu.be/tnQKhCV5jRg?si=H6zJMSDz6Hyn3Dc0

[Digger Don]

Thanks, barbender. I think you confirmed what I was thinking. That video was interesting, but I don't think I'll be buying one of those any time soon. Don

[barbender]

No, me either! But it illustrates the solution industry has come up with to get maximum recovery out of logs that have sweep in them, without introducing even more stress into the lumber.

[WV Sawmiller]

   Somewhat related to this topic is my policy of never releasing the clamp when I turn the cant to the final face. I make sure the cant is laying flat on the bed rails and clamp it securely below the height of my last board/cut and then I saw to the bed.

   I used to release the clamp when the cant 4-5 inches thick and stand my flitches next to the cant for edging. I found often the cant sometimes had stress and would raise up slightly with the extra weight removed and I could never get the cant back flat on the rails which ruined at least one board making it thick and thin. Now I saw the cant into boards and leave the last 3-4 boards on the bed and stand the flitches next to stack of boards and edge against them. I get the same rigidity with a stack of same width boards as a solid cant.