Assessing stresses prior to resawing

[Josko Catipovic]

I just resawed a (QS oak) plank that popped out like a clamshell and actually split the last couple inches of the plank. Now there is about an inch of space in the middle between the two resawn halves of a 40" 8/4.
What's a good way of assessing whether wood has residual stresses prior to resawing? FWIW, this plank was KD and sat in my shop for a couple of years. Since we just came off a humid summer, it's plausible the outside has a higher MC than inside. I dehumidify my shop to 70% in the summer, and try to keep it above 30% in the winter.

[Jim Becker]

Unfortunately, this is largely a gamble. Most boards would be settled down by that point, but "that one board" does come along and there are often no signs of it. Excessive bowing like you describe is probably an extreme case...it's probably stress from how it was situated in the tree as opposed to a wicked moisture imbalance. IMHO, for what that's actually worth...

[John TenEyck]

There is an otherwise well respected contributor to FWW who said that if you drop your lumber on the floor a few times it will release the inner stresses. Seriously? Anyway, to my way of thinking, stress only gets released when you cut the piece, whether it was there due to an imbalance in moisture (not likely in your case) or in the log itself. Some boards look perfect and then go all wonky when you rip or resaw them. I chalk those up to bad luck. But there are others that will show some twist or bow or cup and those are suspect for misbehaving during machine. With Sapele, I won't buy a board that has any of those visual clues in them anymore because every one I did was a problem. With other woods it's not so cut and dry, but I definitely look for flat and straight above all else when buying lumber.

John

[Andrew Hughes]

I was thinking about the same Fww article John mentions. The only advice I can add is do your best to have the right blade for the cut. Then less teeth and less time in the cut less heat.
Trying to figure out what going to warp badly and what’s not is a little bit voodoo and a bit of superstition.
And anyone who can tell they got it figured out is a sorcerer.

Good Luck

[Ron Citerone]

There is an otherwise well respected contributor to FWW who said that if you drop your With other woods it's not so cut and dry, but I definitely look for flat and straight above all else when buying lumber.

John
I have come to the same conclusion. If I am buying retail hardwood I am looking for straight and flat.

[Rich Aldrich]

For hardwood, If the lumber is properly kiln dried, it is stress relieved. At the end of the drying process the lumber is over dried 3%, then moisturized (direct steam injection) up to about 12% then dried to about 7%. We call it conditioning. This is what we do in our kilns and it really helps. The lumber can still have stress but this process helps a lot. The trick is finding a supplier the does it correctly.

We cut about 70,000 bdft a day and can dry 400,000 bdft at a time as well as predry 400,000 bdft. Most is hard and soft maple. White lumber is our specialty but painted cabinets is killing that market.

[Richard Coers]

White oak is notorious for this. It's extremely hard to kiln dry, the 8/4 makes it even more difficult.

[Josko Catipovic]

I guess I now have two questions: Is there some way, (say if I cut off an inch off one end) to find out if the plank has residual stresses? and 2, Is it possible that a KD plank that sat in the humid shop for a summer build up enough of a moisture gradient to stress like this? Is there a way to check for a humidity gradient in a plank by testing a small piece?

FWIW, this was a QS plank that looked 'bout as straight and nice as any I've seen. There were no significant irregularities outside or (after sawing) inside. It came from a 500 BF batch I got 2 yrs ago through a local distributor (Downes & Reader, now Rugby.)

[John TenEyck]

The tuning fork test will tell you if a board has residual stress in it, but you need to take the sample at least 12" from the end which often makes it impractical. But if you can spare a foot off a piece that will tell you. Look it up in Hoadley's book; probably on-line, too.

It's unlikely your lumber developed stress from differential moisture unless you had a massive change in RH a few days before you resawed that board. A moisture meter would tell you if that was the case.

John

[Brian Holcombe]

Unfortunately, resawing tells the story best. I’ve had lumber that is otherwise perfect and well behaved before resawing turn into material ready for the trash bin, at times. Other times a board you expect up be a handful can saw perfectly.

Typically quartersawn woods will bow and flat sawn will cup. Stuff that has been sitting around the shop for a long time tends to fair better than materiel just in from the mill and recently out of the kiln. As example, I resawed a bunch of 12/4 wide chestnut into chair parts, the material has been sitting since the 1940’s and it has been in the shop a couple months after sitting in my friends shop a couple years. Sawed perfectly, the kerf did not change at all during any of the cutting. If I have the space I will buy material and leave it sit for a while, that same stuff usually works nicely.

If I have a thick board and the results are critical I will saw or plane 1/8” off both faces before resawing. This will help.

[Tom Trees]

Currently making end caps with a 1/2" laminate inbetween 1 3/8" pieces.
I always try to find a piece close to dimension, but have no suitable half inch stock, so I have to resaw them...say at least 35% oversize.
What possibly makes matters worse is having to either store timber in the house or bring it inside and blast it with a heat gun, while its over a new mesh table I made which
sits over the radiator(s)
I am trying to store freshly resawn timbers somewhat closer to the dimentions I need in the house, and clamped together as soon as the're cut.

You can loose a lot of timber not from the initial bowing which is a given and no fun to watch bow before your eyes,
but the fact that you can't properly flatten a thin board using a hand plane without
flipping the board due to material deflection.
Its a lot easier to plane something thicker as it wont deflect, and then glue that to a thicker component which is still oversize
and then cut it after the fact and plane down to spec.

Its nearly all quartersawn stock I have used for the 1/2" laminate as it has nice figure often.
These are always troublesome, which makes me wonder because QS is deemed more stable.
I have gotten away with it before with no deflection though.

I wonder if any folks wet the concave side like what some folks do with sheet goods.
I use regular Titebond and wonder if any problems might occur?

For an interesting giggle have a look at this super productive machine
Does it always work this well me wonders

https://www.youtube.com/watch?v=-AG6tHBj96Y

I have ever heard of hitting the stresses out from a plank, like what engineers do when making precision straight edges before a final kiss.
But this machine sounds like its giving the timber a beating.

Tom

[David Utterback]

I had this problem several years ago with tiger maple. It had been kiln dried and every board acted the same. You might be able to see it in the first couple of inches of the cut but it might be slight.

[Mark Hennebury]

Hi Tom,

The answer to your question: "Does it always work this well me wonders "

Supersurfacers are the same as every other machine; Yes they work like they are supposed to, when they are setup and maintained like they are supposed to be, by people who understand how to operate them.

Does a hand plane work? depends who you ask. Ask someone that knows how to set up a Japanese or western handplane and they will answer you Yes of course they work. Ask someone who doesn't know how to set them up and use them and they will tell you no, they are garbage, cause tearout and jam up with shavings.

I sold that supersurfacer and a knife grinder to that company.
The produce thermally treated hardmaple, Birdseye and curly Maple, not exactly the easiest to finish with a handplane.
We ran a bunch of samples for them, that convinced them it provide the best finish in the most efficient way.
Lots more info on supersurfacers on my Youtube channel https://www.youtube.com/channel/UCPqMmpf55W_GC3VJxlk7xVw if you are interested in learning.


420173420174


https://www.youtube.com/watch?v=INk4ClGnIn8&t=200s


For an interesting giggle have a look at this super productive machine
Does it always work this well me wonders


I have ever heard of hitting the stresses out from a plank, like what engineers do when making precision straight edges before a final kiss.
But this machine sounds like its giving the timber a beating.

Tom[/QUOTE]

[Tom Trees]

Mark
I probably didn't add the video correctly, but before the demonstration of that super surfacer is an awesome gang sawing guessing bandsaw type machine.

On a side note having some oversized sawn timbers to make some 1/2" laminates clamped up in the house seems to have done the trick, and they lay flatter than when resawn,
and still had plenty of meat after planing up 3 faces..will plane to a line on the other face up when out of the clamps.
I think I will continue doing this.

What do folks think about dampening the cupped face?

Tom

[Mark Hennebury]

Hi Tom,

That saw is also a quite fascinating machine; more of a jigsaw than bandsaw, its a thin-cutting frame saw probably a Wintersteiger. pretty slick machines.


https://www.youtube.com/watch?v=3ozRhFIik1w



Mark
I probably didn't add the video correctly, but before the demonstration of that super surfacer is an awesome gang sawing guessing bandsaw type machine.

On a side note having some oversized sawn timbers to make some 1/2" laminates clamped up in the house seems to have done the trick, and they lay flatter than when resawn,
and still had plenty of meat after planing up 3 faces..will plane to a line on the other face up when out of the clamps.
I think I will continue doing this.

What do folks think about dampening the cupped face?

Tom

[Fred Falgiano]

...With other woods it's not so cut and dry...

I see what you did there. 😁