this post was submitted on 08 May 2024
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[–] [email protected] 5 points 6 months ago (2 children)

What is a mil in this context? I'm genuinely curious.

[–] [email protected] -3 points 6 months ago* (last edited 6 months ago) (2 children)

A millimeter i.e a thousands of a meter.

edit: I was wrong, confusingly enough it is a thousands of an inch

[–] [email protected] 4 points 6 months ago* (last edited 6 months ago) (1 children)

In the design and manufacture of PCBs (aka circuit boards) a "mil" is a one thousandth of an inch, so it makes sense that's what is being used in this context.

Also the maths check out: 0.005 inches is equal to aprox 0.12mm, "just over 0.1mm".

[–] [email protected] 2 points 6 months ago (1 children)

I stand corrected, and I see I didn't read the comment thoroughly enough either.

Colloquially as a non-pcb maker I would use and hear the term "mill" as short form millimeter so I assumed it was that.

so TIL :)

[–] [email protected] 3 points 6 months ago

Yeah, I found it wierd too when I started designing PCBs (as hobby) that "mill" actually stood for thousanth of an inch.

Probably for historical reasons, there are tons of things in the older domains within electronics that are based on inches rather than metric units: for example the spacing between the legs of a microchip in the older chip package formats (so called DIP, the ones with legs that go into holes) is exactly 0.1"

The sizes in more modern electronics isn't usually based on inches anymore, but circuit boards are old tech (even if done with new materials) so there are still a number of measures in there which are based on inches.

[–] [email protected] 9 points 6 months ago (1 children)

5 mm isn't 'just over 0.1 mm'. That can't be right.

[–] [email protected] 4 points 6 months ago

Well, it depends on your margin of error.

[–] [email protected] 13 points 6 months ago (3 children)

Probably one thousandth of an inch.

[–] [email protected] 6 points 6 months ago (2 children)

I've heard it referred to as 'thou' but not 'mil'

[–] [email protected] 3 points 6 months ago* (last edited 6 months ago)

A couple old metrology equipment dated back from the 80s I still use calls them 'mil'. It's got dual dials for mil/mm. Gets me confused sometimes because the gauge can go down to couple millionths of an inch/couple 10s of nanometers.

LVDT for those curious.

[–] [email protected] 2 points 6 months ago (1 children)

Yeah, I’ve never heard of that before either. What I have heard of is either MOA or MIL reticles. In that context a Mil stands for milliradian, which is a representation of angle. That definitely doesn’t track with the post though.

[–] [email protected] 4 points 6 months ago

And it's especially confusing for people who use sane measurement systems where "mil" is short for "millimetre", because it's just the start of the word. I think anyone that still insists on measuring things in thousandths of an inch should keep their own bespoke lingo too, and everyone else should steadfastly refuse to acknowledge "mil" in this context.

[–] [email protected] 10 points 6 months ago (2 children)
[–] [email protected] 1 points 6 months ago

Hey thousands of an inch are the only part of our imperial system that actually makes sense

[–] [email protected] 4 points 6 months ago