Thickness of hardwood for woodwork?

[Andreas Andersson]

Hello.

When sawing hardwood timber to be later used for woodwork / furniture,
is there an optimal thickness to prevent cracks, when drying?
Or do hardwood crack when drying regardless of thickness sawn?

[roger wiegand]

Utility at the end is what counts. You could cut 1/2" lumber, and it might dry faster or better, but it wouldn't be much use-- certainly not after you joint and plane it flat. 4/4 is minimal, I try, whenever possible to buy 5/4 to still be able to get a slightly heavier member despite the wood not being completely flat. Thicker lumber, of course, brings premium prices.

[Maurice Mcmurry]

I have been getting re-fimiliarized with the WoodMizer and go by the quarters scale the thinnest being 4/4, unless I am sure that I want thinner lumber for a special project. I try to maximize the log by making 4/4, 6/4, and 8/8. I just made a bunch of Oak and Locust 6 inch X 6 inch posts. I cut 4/4 and 6/4 to get the logs down to 6 inches and 12 inches, then cut for the 6 X 6s.
4/4 dries faster, warps and checks worse than 6/4, particularly in the outer slab cuts.
Missouri Pacific lumber is close by. Their 10 acres of stacks of big beautiful Walnut are mostly 8/4.

[Greg Parrish]

I have learned to stay at 5/4 minimum on our mill, but 8/4 is preferred. We’ve cut white oak and cherry, and the thicker pieces stay square better. The thinner are more prone to check and twist as Maurice mentioned.

[John TenEyck]

Nothing is w/o compromise. 4/4 dries faster than thicker lumber but is more likely to warp if not well stickered. 8/4 has less tendency to warp but more to split, plus it takes much longer to dry, whether that be air or kiln drying. That's one reason 8/4 is more expensive per BF than 4/4.

The best thing to prevent splitting/cracking is to coat the ends of logs with wax emulsion as soon as the tree is felled and to cut the log into lumber asap. Alternatively, putting the logs in a pond until they can be cut is effective, too. Kiln drying offers better control than air drying, so splitting is less of a problem, but air drying can successfully be done as long as the drying stays within the allowable rate for that species. That's not too hard to accomplish if the lumber is cut in the early Spring or in the Fall where I live in the NE, but sometimes nearly impossible if it's cut when drying rates are very high, typically in the late Spring through Summer. White oak, in particular, is subject to checking or worse when air dried.

To answer your question, I cut what I need, which means 4/4 up to 10/4. When I cut 4/4 I try to make very uniform stacks and as high as I can stack it, so the mass of the stack keeps the boards from warping.

John

[Jonathan Pace]

I agree with Greg Parrish. I've also discovered that 5/4 is the minimum, with 8/4 as a better option on our mill.

[Richard Coers]

Doesn't it depend on species? 8/4 white oak is very difficult to dry, so a great advantage to cut it thinner as an example.

[Greg Parrish]

Doesn't it depend on species? 8/4 white oak is very difficult to dry, so a great advantage to cut it thinner as an example.

I'm sure that's a true assessment. Our milling operation hasn't gotten that sophisticated yet. LOL

We picked up a 23" Frontier mill from Norwood last year to start learning. We are dealing with yellow pine, white oak and a few other hodge podge mixed in tree types on our property. We are air drying, but we are also playing with a poor mans kiln of sorts. We setup a 20' cargo container with a center divider and a vent and fan pulling air through the box across the stack. This wasn't really for drying but for bringing a stack to temperature to kill bugs and set pitch. Haven't tried it yet, as it really has only a 4 month or so window during the summer that it will generate enough heat inside. But, worse case scenario if it doesn't work the way we want, we can always revert the container back to a storage building. Nothing lost for trying the idea.

[John TenEyck]

Doesn't it depend on species? 8/4 white oak is very difficult to dry, so a great advantage to cut it thinner as an example.

Yes, exactly. Checking and honeycombing is more likely as thickness increases because the probability of the surface drying before the interior is so much higher, and that creates stress which, beyond some value, causes defects. Species like white oak are especially prone to the problem for the same reason it is so rot resistant. There's no good reason to cut 8/4 white oak, or any species for that matter, unless you need 8/4.

The Forest Products Lab of the USDA has a very comprehensive document on drying hardwood here: https://www.fpl.fs.usda.gov/documnts.../fplgtr118.pdf

John