[sdiy] Metric vs imperial, was: My new Moog 960 sequencer clone module project.. slowly but surely ..

[thresholdpeople]

I'm with Don on this one - there are advantages and disadvantages to both. It depends on application.

Sure standard is a bit wonky for lots of stuff, certainly formerly more egalitarian. But if you look at any industrial field, the jargon and standards of that industry also have arcane and nonsensical standards which are ingrained, when from the outside looking in. TIG welding torch accessories, lathe tooling inserts, nearly everything in sewing machines, etc etc. All rely on semi-arbitrary jargon defined a long time ago by someone, or a group of individuals, to whom it made perfect sense. Everyone else now just has to learn it.

For your machining example, I'm in NYC, but get drawings in both metric and standard, and while I'm certainly more comfortable with inches - i.e. I can gauge what an inch looks like, but when I see a random 16mm callout, I have to think and remember that 12.something millimeters is a half inch or so etc etc.. of course that's on me.. there are those for whom it's the opposite and those that are perfectly fluent with both.

That being said, for tight tolerance machining work there is a bit more - simpler - resolution in using inches. The difference between 0.001" tolerance (aka 0.0254mm) to say 0.002" (0.0508mm) or 0.003" (0.0762mm) (which is a more common next step from 0.001") requires one fewer decimal place and is a neater number, I definitely prefer tight tolerance work in inches, again, likely a personal preference, but I do think it makes sense.

I'm surprised you didn't call out the silliness of 0.001 inches AKA "a thou" AKA "one mill". A mill is not a millimeter. That definitely screws people up!

Furthermore, I get where you're coming from with the drilling example - standard has fractional drills, wire gauge drills - AKA the numbered ones, and letter drills. However, sure an M4 screw needs a 3.5mm drill bit, but for almost every other metric screw size that ratio is not consistent, furthermore it also often varies from fine to coarse threads (same as in standard). So really it's still a memory thing, just like someone who works with 8-32 all the time just has #29 memorized.

And when you consider wood working, now mind I'm not a super sophisticated wood worker, nor carpenter, however, those units, when in standard, are typically fractional, as the possible tolerances are completely different... There is no need for decimal, and sure it could just as easily be in millimeters, but in a practical no need for millimeters with decimal places (which, also, I've never seen micrometers, err micron used in a way that the conversion between centimeters and millimeters works - i.e. I've seen 10 millimeters and 1 centimeter quite commonly interchangeable, but I've rarely seen callouts for 100 microns, though 0.1 mm is very common.. maybe only for applications involving optics and lasers, and now commonly 3D printers) as to Don's point it all depends on application.

I'd say there is an inherent facepalm in the fact that the US standard Foot (12 inches) is based on a metric conversion from the late 19th century. That's kinda dumb.. couldda just stuck with metric, but it also means that the two units have an inherent way to translate them. Also most wood here in the US while nominally a fractional thickness is still actually in millimeters.. errr though the sheet length is in inches..

I certainly don't enjoy mixed unit systems. A friend told me that certain older British cars have standard, metric, and a few other arcane units all in one vehicle.. Problematic when reaching for a wrench I guess.

How about something like mic stand thread standards? The metric ones are still in imperial threads! I recently learned that, and that's quite odd.

And hell, aren't nearly all electrical component pin spacings in standard?

Audio connectors.

Largely it's whatever industry-standard gained adoption.

Let's face it, all and any unit of measurement or designation was at some point arbitrarily set and then gained wider adoption. That's why I think it's funny/ironic that standard is also known as imperial. Though, I'd say metric has certainly captured more at this point. Anyway, this is all a parallel discussion to a linguistics discussion. When you get right down to it, these ingrained modes of understanding place certain restrictions around what's capable to think and understand.. again to Don's point of it's application specific. When you embrace you different things for different applications it's a bit easier to be less rigid, thus less ingrained in thinking.


‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Wednesday, November 11, 2020 8:11 AM, Tom Ivar Helbekkmo via Synth-diy <synth-diy at synth-diy.org> wrote:

> Donald Tillman don at till.com writes:
>
> > Of course I recognize and appreciate the advantages of the metric
> > system. It's great for scientific work. But for everything else;
> > engineering, design, culture, regular life... the metric system
> > becomes a serious disadvantage.
>
> It depends. You mention engineering. Talk to a machinist, working in
> the United States, and he'll tell you that while material stock comes in
> Imperial units, fastener sizes are specified in standard fractions of
> inches, and so forth, all his actual machining work is done with the
> "thou" as the base unit. A thou is 1/1000 of an inch. A milli-inch,
> that is, but it's pronounced "thou". (For real precision work, it's
> necessary to consider "tenths" as well, where a tenth is 1/10000 of an
> inch.) A machinist will say things like "this needs to be 500 wide",
> not "half an inch wide".
>
> (As an example of an engineering advantage of metric standards, if
> you're drilling a hole that's to be tapped for a standard #8-32 screw
> thread, you need to use a .136 drill (also known as a #29 drill). There
> are tables to look this up. For a metric M4x0.5 screw (very close to an
> #8-32 in size), I don't need a table to know to use a 3.5mm drill.)
>
> Also: "serious disadvantage"? Only to the extent that you're either
> working with tools and material that are in Imperial units, or you've
> grown up with Imperial units, and have no intuition for the metric.
> That's just saying that trying to change confers disadvantage, which of
> course it does. It's not an inherent problem with the metric system.
>
> You sound like one of those people who go "Metric? Hah! When people ask
> me how far it is to the post office, I say 'about a mile'. I don't say
> 'about 1.609 kilometers'", and think they've made a valid argument.
>
> -tih
>
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