So you can see in this picture here, the drawing says 2"X4" Lumber but the drawing shows 1.5"X3.5" size. Does this mean we have to cut it down to that size or is 2"X4" lumber really 1.5"X3.5"?
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2x4 lumber is actually 3.5x1.5 atleast here in the U.S.A. Not sure about other countries though.
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2x4’s in the US are 1.5"x3.5"
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Another of the many joys of robotics, is seeing folks learn what a 2x4 really is
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I remember learning about this when I was about 8 years old. I spent so long pondering why in fact a 2x4 who gets its name sake from its dimensions was not actually 2x4. I didn’t understand marketing back then.
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It’s not really marketing. The naming comes from the fact that it would be saw cut to 2 x 4, dried, and then milled down a quarter inch on all sides (more for larger sizes) to get it straight and smooth, and give it those nice rounded corners.
You can still buy saw cut (unfinished) lumber that is closer to the named size, but due to modern process improvements 2x4s don’t really start at 2 x 4 anymore.
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And…
1/4" polycarbonate is 0.21" (most of the time)
1/2" plywood is 15/32"
2-1/2" pool noodles are around 2.3"
Andy B.
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I’ve always thought that’s just kinda the justification that lumber sellers use. In reality 2x4 has been a common size for a very very long time and a while back it did in fact used to be 2x4 (was just sold unmilled) as opposed to the 3.5x1.5 it’s commonly found as today. The lumber manufactures just figured that since both 2x4 is a classically recognizable name and rolls off the tongue a lot better than 3.5x1.5.
There have been reductions by lumber manufacturers in the 50s and 60s to get to today’s standard, but originally the difference was due to green vs dried & planed wood. From Wikipedia:
Historically, the nominal dimensions were the size of the green (not dried), rough (unfinished) boards that eventually became smaller finished lumber through drying and planing (to smooth the wood). Today, the standards specify the final finished dimensions and the mill cuts the logs to whatever size it needs to achieve those final dimensions. Typically, that rough cut is smaller than the nominal dimensions because modern technology makes it possible to use the logs more efficiently. For example, a “2×4” board historically started out as a green, rough board actually 2 by 4 inches (51 mm × 102 mm). After drying and planing, it would be smaller by a nonstandard amount. Today, a “2×4” board starts out as something smaller than 2 inches by 4 inches and not specified by standards, and after drying and planing is reliably 1 1⁄2 by 3 1⁄2 inches (38 mm × 89 mm).
Also be careful of the lengths. Sometimes the lumber is slightly longer than the denomination, especially for the longer lengths. For example, 16’ boards may be an inch or more longer than 16’.
Lowes lost a law suite over this in California. I guess you can no longer buy 2x4s in CA. I wonder what they are going to do when they figure out that 1-1/4" pipe really isn’t not 1-1/4" Good in finding it in metric.
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The lawsuit requires them to list the actual dimensions on the tag. You can very much still buy 2x4 here in California. It says 2x4xH in big numbers and the actual dimensions lower down on the tag. I’ll snap a picture next time I’m at a hardware store if I remember.
Despite the Lowe’s case, there’s at least a dozen more of these lawsuits all across the U.S. that have been thrown out (including a judge who said “no reasonable consumer would think that the labels showed the exact dimensions of the lumber.”
That judge clearly took a shop class in school. This is something I learned in like 7th or 8th grade in the mandatory woodshop class. We also rotated through “electives” like home ec, and music.
This year I bought my lumber at Lowe’s who still sells 2x4s whereas Home Depot sells 1.5x3.5s. It’s the same lumber, but a matter of principle for me. When you’ve grown up building things from “tuba-fors” it’s just not the same to build it from a 1.5x3.5.
If you did FLL, you knew it.
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“Welcome to American Lumber”
That’s what my engineering teacher told me when I asked him the exact same question.
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