xkcd #3138: Dimensional Lumber Tape Measure
Title text:
A person with two watches is never sure what time it is, especially if I got them one of the watches.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3138/
Huh, the explain link says the dimensional sizes originated from the wood being cut at the listed size while green, then shrinking as it dried. I was told that it was done for construction purposes, where the wood would likely be covered by plywood or drywall that would bring the dimension up to size. I never questioned it before; that always seemed plausible enough.
There is no sensible reason to sell something as a dimension before it's ready to sell, a 2"x4" should be so when sold, not when curing, it takes nothing to cut oversize to accomodate for shrinkage, or to cure and cut later at the right dimension
The carpenter or woodworker cares about how big the board is. The sawyer cares about how much of the tree it took to make that board. The lumber yard has to make those two ends meet at a price point.
If you sell me a 2" by 4" board, you cut it 2"+the width of the sawblade, just like the metric boards are sold.
Also is a saw really 1/2" wide? That's like 1.27cm, that's wild.
If you really really cannot sell a true 2"x4" at the price of a 1.5" x3.5", just keep the same price and call it what it is.
These boards are factory planed, not sawn.