How does that work when wood varies due to moisture content? If they give precise mm measurements, only 20% of boards will meet those criteria.
Comment on 2x2 lumber at Home Depot is now 1.28x1.28. Nominal size is supposed to be 1.5
cosmicrookie@lemmy.world 7 months agoNo its not Maybe in the US? At least here, it is and has to be, very precise especially when it comes to industry quality. It is precise down to the mm!
SchmidtGenetics@lemmy.world 7 months ago
captain_aggravated@sh.itjust.works 7 months ago
Construction lumber, especially pressure treated lumber, is sold so wet I don’t think it really matters. I’ve actually never tried to calculate wood movement for construction lumber because who the fuck cares? But for furniture lumber which is dried to between 6 and 14% moisture, there is a formula:
width of the board in inches x percentage of moisture change * expansion coefficient for a particular species.
Yellow pine (extremely common construction lumber) has an expansion coefficient of .00263. A 2x4 (actual dimension 1.5" by 3.5") that undergoes a 4% moisture content change will grow/shrink 3.54.00263 = 0.03682 inches, or just over 1/32". That’s in width; it’ll vary by less than half that in thickness. Wood basically doesn’t move along the grain; the board won’t get appreciably longer or shorter.
sukhmel@programming.dev 7 months ago
Maybe they mill, store, and sell under the same moisture conditions?
Also, how big is the difference in size and moisture for the same piece of wood? I would expect that moisture is usually not higher than 90% and not lower than 10% or something like that, but don’t know how it really is
SchmidtGenetics@lemmy.world 7 months ago
Once it leaves the mill they go to various stores and regions with different conditions.
Once I buy it at the store and take it the site, it’s now different from the store. You should acclimate all lumber for 48 hours before using it as well, this is so the wood doesn’t swell to shrink more after installing it.
captain_aggravated@sh.itjust.works 7 months ago
A yellow pine 2x10 might move a tenth of an inch, not a full inch.
sukhmel@programming.dev 7 months ago
So, more than 10% difference, that’s enough to be a problem, indeed
Auli@lemmy.ca 7 months ago
Bullshit. Wood expands and contracts so ther is no way you can be precious down to the mm.
Thorry84@feddit.nl 7 months ago
That’s why the standards specify the moisture content of the wood as well as the dimensions. This is even the case for US standards.
intensely_human@lemm.ee 7 months ago
I’ve not really encountered this wood expanding and contracting thing. Are you sure?
captain_aggravated@sh.itjust.works 7 months ago
Absolutely sure. It’s not really a factor in construction because of how the structure is engineered, but woodworkers have to constantly think about it.
Wood expands and contracts across the grain, but not so much along it. If you take a board that has been in a dry environment, put it in a humid environment, and allow it to acclimate, it will increase in width and thickness but not in length. At the microscopic level, wood is kind of like a bunch of ropes glued together with sponge, as it soaks up water the sponge wants to expand but the ropes don’t let it expand along their length.
Us woodworkers have to think about that when building things like doors, which might fit fine in the winter and then stick in the summer. It’s why we build frame and panel doors like this:
The large panel in the middle can expand and contract so much that it might be a problem, so we literally put it in a box. The outer dimensions of the frame are made mostly of the length of boards so it won’t expand and contract much, and the panel rests in a groove in the frame, not nailed or glued in place so that it can safely expand and contract as it wants to.
Attaching wide boards end-to-face can even present a situation where the boards want to move in different directions and they’ll eventually break each other.
You can even calculate the amount of wood movement given the species, of the wood, the dimension of the board and the amount of moisture change, you can read about it here.
SchmidtGenetics@lemmy.world 7 months ago
usualsuspect191@lemmy.ca 7 months ago
True, but the amount they shrink and grow across the grain tends to be proportional. A 2x4 is very rarely measurably different from 1.5"x3.5", but a 2x10 (like you’ve shown) is 1.5"x9 1/4" but is often anywhere between 9 1/8" to 9 3/8"
AnUnusualRelic@lemmy.world 7 months ago
That’s crazy, how can you make a profit if you give the customer the exact measurement? You have to saw a bit off and pad your earnings!
pearsaltchocolatebar@discuss.online 7 months ago
That’s not why there’s a nominal size vs actual size.
BruceTwarzen@kbin.social 7 months ago
Yeah but they measure in feet and cheesburgers.
conditional_soup@lemm.ee 7 months ago
And lies, don’t forget the lies
BossDj@lemm.ee 7 months ago
Alternative facts, thank you very much
Aceticon@lemmy.world 7 months ago
In bullshit, which is itself an imprecise metric.