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/
And that’s what men the world over use to measure their appendage!
I feel this was the true decline of America.
Interestingly enough, this concept was used in pattern making for casting machine parts back before modern machining and parts manufacturing.
They were colloquially called shrunk rulers, and looked like a standard ruler, but was actually longer to account for the shrinkage of the material being cast.
For example, say you’re casting a part from iron, which shrinks 1% as it cools, which amounts to 1/8 inch per foot.
An iron shrink rule would look standard, but actually measure a foot as 1 foot 1/8 inches to account for the shrinkage (this is an example and not meant to be actually accurate).
Source: am historian that interviewed pattern makers that used shrink rulers in their work.
It shrinks? Like a frightened turtle!
Neat!
Can still work as long as you use the same ruler and just use referenced measurements.
That 8” mark though 😂
That will go nicely with a tape measure that uses the Chinese inch (cùn), which is equal to 1.312 imperial inches
This hurts so bad to think about
Which part? The ruler that can’t exist or the part where finished lumber is smaller than the listed size?
Eh, not a problem at all. You can’t make it look exactly like my other three and I make sure to use the same tape measure throughout a project, really after the first couple cuts I’m not even using it I’m using the cut pieces to measure against.
I don’t care what the number actually is, just that I can mark in the same spot consistently.