Comment on xkcd #3138: Dimensional Lumber Tape Measure

harsh3466@lemmy.ml ⁨1⁩ ⁨week⁩ ago

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.

source
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