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delta_p_delta_x

> 1/10th of a thou

What is this unit?

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The standard industry term for a thousandth of an inch. Also called a mil.

https://en.m.wikipedia.org/wiki/Thousandth_of_an_inch

A 1/10th of a thou is 1/10000th of an inch, or 2.54 micrometers. It's insanely small.

> a thousandth of an inch. Also called a mil

Why, America... At that point, if it's inventing new units to decimalise USC units, why not just use micrometres?

Or they could stick with binary and introduce a name for 1/1024th of an inch. Borrow a meme from the “almost SI” prefixes kibi, mebi, gibi etc., and call it a mibi, perhaps? ;-)

What the hell are kibi and gibi?

Kibibyte: 1024 bytes. Gibibyte: 2^30 or 1,073,741,824 bytes. The -bi suffix is intended to signify “binary”.

They are IEC prefixes, complementary to the SI prefixes, and they only are defined for positive exponents.

  kibi : ki : 2^10
  mebi : Mi : 2^20
  gibi : Gi : 2^30
  tebi : Ti : 2^40
  ...

Conveniently, these numbers are fairly close to 10^3, 10^6, 10^9, and 10^12 respectively (but with increasing error: 2^40 is almost 10% larger than 10^12, whereas 2^10 is only 2.4% larger than 10^3).

This leads to a lot of conflation, mess, and misreporting by vendors and OS authors. Windows is an egregious example. A 1 TB (terabyte, 10^12) disk is reported in Windows as 931.7 GB. It ought to be 931.7 GiB, which is what Linux does. macOS uses the correct number but SI prefixes, so 1 TB is reported as 1 TB.

Wait, does MacOS report file sizes in base 10 as well, or just disks?

File sizes too.

I think it's hard to call it misreporting when they've been reporting it the same way since before the standard you'd rather they use existed.

Electronics manufacturing uses both with about equal frequency, often without unit names attached, and it's confusing as all hell, at least as a hobbyist. E.g. a 0603 footprint can mean 0.6×0.3 mm or 60×30 mils.

https://eepower.com/resistor-guide/resistor-standards-and-co...

Because at the time of the invention and adoption of this term of this term in the late 1850s, the metric system didn’t have widespread adoption at all. The treaty of the meter wasn’t until 1875.

So the metric system and decimalization of the inch are roughly contemporaneous and “just use this othe, also brand new system” isn’t an obvious choice at that point.

Fair enough.

I think the real question is... Why is such a unit still being used? I was under the impression that any serious ultra-precise CAD and machining was done in milli, micro, and nanometres. I thought pretty much any serious science or engineering had been metricated...

But then again I shouldn't be surprised; Americans measure the volume of lakes in 'acre-feet'...

I mean, a "thousandth" of an inch is also a decimalised USC unit.

Don't try to logic how Americans measure things.

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