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Thousandth of an Inch

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Re: Thousandth of an Inch

#41

Post by Jedd »

kazinator wrote: post #39
seniorsassycat wrote: post #18

Curious why we jump from 16ths or 32ths to thous rather than 64ths, 128ths, 256ths, 512ths and 1024ths I guess they are a mouthful without good abbreviations and there was a tech jump between woodworking and machining so in betweens aren't used

Mils are awesome for wire thicknesses, trace widths, pin spacings on circuit boards, fine drill bit sizes for through holes ... Guitar strings are, e.g. 9 to 46: .009" high E, .046" low E. Classic DIP (dual in-line package) integrated circuits and headers have 100 mil spacing: ten pins per inch. IIRC, you drill a 25 mil hole for the pins. This is international. The metric system doesn't have a nice mil-like unit for…

> The metric system doesn't have a nice mil-like unit for those scales; the millimetre is way too crude, and micrometres are too fine.

This kind of absurd claim would be more compelling if you hadn't just used 3 decimal places and a quotation mark to define a distance in a format used by at most ~5% of all the people working in such scales:

> ... 0.046"

My point - metric can also use decimals. More adroitly, too, I'd argue, because of the consistency.

Re: Thousandth of an Inch

#42

Post by klodolph »

taneq wrote: post #40
klodolph wrote: post #22

Earlier quoted context omitted.

Ounce / fluid ounce is roughly the same as gram / milliliter. A fluid ounce of water weighs about one ounce (1.04 oz/fl oz or something), like a milliliter of water weighs about one gram (0.997 g/mL or something). The US customary units are pretty logical, they're just not powers of 10.

> Ounce / fluid ounce is roughly the same as gram / milliliter. That's how it's used, but the units don't measure the same thing. It's like measuring an engine's power output in square meters, because a kilowatt is about a square meter of sunlight.

> That's how it's used, but the units don't measure the same thing.

I'm having some real trouble parsing this sentence right here. You're saying that the two DIFFERENT UNITS "fluid ounce" and "ounce (weight)" measure DIFFERENT things? Yes, different units measure different things. Or maybe I don't understand what you are trying to say here.

If I said "kilogram force", you'd know exactly what that is.

You are also not confused when I say that water boils at 100 degrees centigrade, and a right angle is 90 degrees.

And don't even get me started on the number of people who argue that 1024 bytes is called a "kilobyte".

Re: Thousandth of an Inch

#43

Post by deathanatos »

TheSpiceIsLife wrote: post #33
stephen_g wrote: post #31

The most annoying thing about the thousandth of an inch is while it’s often called a ‘thou’, it’s also called a ‘mil’ which sounds exactly as the common slang for millimetre (mill) here in Australia at least (used more often in construction, but it’s still common so makes it confusing). Luckily we don’t really do PCB design in imperial anymore at any of the companies I’ve worked with (I hear even US companies are mov…

You're not going to say 20 mil and the context not be clear if you mean 0.508mm or 20mm, are you?

Now's where one needs the Wikipedia article titled something like "Engineering Failures Caused By American/Metric Confusion".

There's at least https://en.wikipedia.org/wiki/Mars_Climate_Orbiter and TBH I was hoping there'd be a link to such a list on that one.

I seriously hope I'm Poe's Law-ing your post too, and there's an implied /s on there, because if you could see the level of communication effort I see at work … yeah, I'd absolutely believe that someone would use it in a confusable context.

Re: Thousandth of an Inch

#44

Post by dwaite »

klodolph wrote: post #22
taneq wrote: post #17

Earlier quoted context omitted.

I think it was all over once America started using ounces to measure volume.

Ounce / fluid ounce is roughly the same as gram / milliliter. A fluid ounce of water weighs about one ounce (1.04 oz/fl oz or something), like a milliliter of water weighs about one gram (0.997 g/mL or something). The US customary units are pretty logical, they're just not powers of 10.

> The US customary units are pretty logical, they're just not powers of 10.

It somewhat slides off the cliff when you take into account the existences of the imperial ounce and the US food labelling ounce, though.

Re: Thousandth of an Inch

#45

Post by klodolph »

dwaite wrote: post #44
klodolph wrote: post #22

Earlier quoted context omitted.

Ounce / fluid ounce is roughly the same as gram / milliliter. A fluid ounce of water weighs about one ounce (1.04 oz/fl oz or something), like a milliliter of water weighs about one gram (0.997 g/mL or something). The US customary units are pretty logical, they're just not powers of 10.

> The US customary units are pretty logical, they're just not powers of 10. It somewhat slides off the cliff when you take into account the existences of the imperial ounce and the US food labelling ounce, though.

The US uses the US customary units and metric, not the imperial units.

Not that it matters much, since the US customary ounce and the imperial ounce are the same mass. Maybe you're thinking of the fact that an imperial pint is different from a US customary pint?

Re: Thousandth of an Inch

#46

Post by kazinator »

Jedd wrote: post #41
kazinator wrote: post #39

Earlier quoted context omitted.

Mils are awesome for wire thicknesses, trace widths, pin spacings on circuit boards, fine drill bit sizes for through holes ... Guitar strings are, e.g. 9 to 46: .009" high E, .046" low E. Classic DIP (dual in-line package) integrated circuits and headers have 100 mil spacing: ten pins per inch. IIRC, you drill a 25 mil hole for the pins. This is international. The metric system doesn't have a nice mil-like unit for…

> The metric system doesn't have a nice mil-like unit for those scales; the millimetre is way too crude, and micrometres are too fine. This kind of absurd claim would be more compelling if you hadn't just used 3 decimal places and a quotation mark to define a distance in a format used by at most ~5% of all the people working in such scales: > ... 0.046" My point - metric can also use decimals. More adroitly, too, I'd…

That 0.046" is just called 46 mils though, or just 46 when that is understood. Those guitar strings are just "nine to forty-sixes" and that's it.

If you're routing a circuit board, you have a grid that is a multiple of the mil: e.g. 25 mils, so if have a part with 100 mil pin spacing, that is four grid lines. Trace widths are multiples of a mil: 6 mil, 8 mil, ... through holes are mils: 25 mil, 40 mil, ... no decimal point or " mark in sight.

Sure, a tenth of a mm would be a useful unit. Problem is, 0.1 mm has no name. It's either 0.1 mm or 100 microns, which are too small. I've not seen anyone define such a unit in practice; they just plod along with multiples of 0.1.

Re: Thousandth of an Inch

#47

Post by metaphor »

taneq wrote: post #14
swighton wrote: post #5

What I find amazing is that one thousandth of an inch is not particularly precise when it comes to machining. You can easily make parts to that accuracy with common mills and lathes. Also surprisingly (to me) is if you have a pin that goes into a hole that is 1-2 thousandths of an inch larger than the pin, it feels like a sloppy loose fit. If you want the pin to feel like a really nice smooth fit you need more like a…

You can do it on common equipment but I dunno if I’d call it “easy.” There’s a reason that +/- 0.05mm costs a lot less than 0.02mm.

This.

For the unindoctrinated, this concise Typical Tolerances of Manufacturing Processes reference[1] may be useful towards establishing pragmatic expectations for manual processes.

[1] https://mae.ufl.edu/designlab/Lab%20Assignments/EML2322L-Tol...

Re: Thousandth of an Inch

#48

Post by BerislavLopac »

deathanatos wrote: post #43
TheSpiceIsLife wrote: post #33

Earlier quoted context omitted.

You're not going to say 20 mil and the context not be clear if you mean 0.508mm or 20mm, are you?

Now's where one needs the Wikipedia article titled something like "Engineering Failures Caused By American/Metric Confusion". There's at least https://en.wikipedia.org/wiki/Mars_Climate_Orbiter and TBH I was hoping there'd be a link to such a list on that one. I seriously hope I'm Poe's Law-ing your post too, and there's an implied /s on there, because if you could see the level of communication effort I see at work…

Oh this is my cue to share my favourite story stemming out of this confusion, the story of the Gimli Glider [0]. It is full of incredible events, each of which would be a good story in its own right - and it still has nothing to do with our favourite Dwarf.

[0] https://en.wikipedia.org/wiki/Gimli_Glider

Re: Thousandth of an Inch

#49

Post by kotenshu »

swighton wrote: post #5

What I find amazing is that one thousandth of an inch is not particularly precise when it comes to machining. You can easily make parts to that accuracy with common mills and lathes. Also surprisingly (to me) is if you have a pin that goes into a hole that is 1-2 thousandths of an inch larger than the pin, it feels like a sloppy loose fit. If you want the pin to feel like a really nice smooth fit you need more like a…

Which is why a more common unit in imperial machining is the "tenth", which is one ten thousandth of an inch.

Re: Thousandth of an Inch

#50

Post by BeFlatXIII »

Jedd wrote: post #30
seniorsassycat wrote: post #18

Curious why we jump from 16ths or 32ths to thous rather than 64ths, 128ths, 256ths, 512ths and 1024ths I guess they are a mouthful without good abbreviations and there was a tech jump between woodworking and machining so in betweens aren't used

Yeah, it's a bit of weird disjoint. Almost a tacit admission, in fact. I've heard that in some crazy parts of the world - say 95% of the planet - it's base-10 all the way down . Makes you wonder if they're on to something with that kind of whacky scheme. Hopefully it works out for them.

How do they measure out ⅓ and 1/6 and 1/12 using only base 10?
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