American measurements

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I had to go back and re-read the history of dimensional lumber. 2x4 was an actual 2x4 cut until recommendations by the Forest Products Laboratory (American Lumber Congress?) in 1919 to balance functional and economic requirements (1 5/8 x 3 5/8). It's neither the shrinkage nor just milling after drying (and if my last 20 trips to big box stores with lumber are any indication, they don't care about cupping or warpage).

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Yup, that was wrong.

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That's why pools are so expensive.

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Worse still, the pattern does not continue like one would expect.

Nominal: 2x4 -- Actual: 1.5" x 3.5"
Nominal: 2x6 -- Actual: 1.5" x 5.5"
Nominal: 2x8 -- Actual: 1.5" x 7.25"
Nominal: 2x10 -- Actual: 1.5" x 9.25"
Nominal: 2x12 -- Actual: 1.5" x 11.25"

There's just an arbitrary point where they decided to take an extra 1/4" bite out of it. I'm not sure whether that's more of an effect of shrinkage from kiln drying being proportional to the original length or an effect of industry practice to mill smaller boards to eke out more cuts per tree.

And for the record, yes, I am aware the discrepancy is not entirely explained by shrinkage. They do a planing step after drying. But the shrinkage is a not insignificant part of it. They have to round down to the nearest convenient dimension from wherever the shrinkage stops.

If longer boards shrink more, the finished boards would necessarily have to be smaller. I question whether that's the effect at play, though, because I believe there was a phase in the industry where that extra quarter inch wasn't taken off, and they changed their minds about it later.

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Yeah whenever I need lumber I plan to set aside at least half an hour to dig through the piles to find OK boards.

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You got the leap year rule wrong.

Every fourth year unless the year is divisible by 100 unless the year is also divisible by 400

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You got the leap year rule wrong.

Every fourth year unless the year is divisible by 100 unless the year is also divisible by 400

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You got the leap year rule wrong.

Every fourth year unless the year is divisible by 100 unless the year is also divisible by 400

And it's a leap day that's inserted, not a leap year

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metaphor

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But wait, those might be metric dicks.

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Hey, you, get back here!