# Metric or Decimal..accuracy?

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Interesting again! Thanks for that info.

Nick

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A bit of tolerance is allowed!

Nick

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Apparently no accuracy either.

Explain the point you're trying to make. You can't because you don't have one.

You really are stupid.

I forgot. Weight changes depending on the unit you use, and in your broken logic length and volume also change depending on the units you use.

Good one.

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Maybe I'm making a dam or building an airplane.

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Well...if you are going to use a tape measure, I know of none that are graduated any closer than 1/16" along the entire length. You might find one graduated in 1/32" for the first 2', but even at that, a comparable metric tape would be graduated to 0.5 mm.

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I guess that his point is that U.S. customary system is not and SI is a coherent system of units.

-- Sincerely yours Zatoichi

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Roger

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_ How about 1/3 or 0.3 ? THAT is the meaning of coherent system of units. You don't have to specify in which units is your data. Everybody knows it's the meter.

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My two cents:

In the late 80's we got drawings for an exotic water-cooled piece of Russian (er, Soviet) electronics.

On the drawing was the spec for the threads used to deliver water to/from the device. It was metric and had 4 decimal places of precision specified.

We start calling local, national, and finally international threaded fitting manufacturers and they say that the numbers do not match up to any known plumbing system.

Then the device actually arrives in the shop and it's obvious: the connector is a perfectly standard garden hose :-).

Tim.

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LOL

John

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And I'm sure you think that an ounce of lead weighs the same as an ounce of gold.

Steve.

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The message from "SteveF" contains these words:

It does, 1oz of lead weighs exactly the same as 1oz of gold.

1oz troy of lead weighs the same as 1oz troy of gold. Are you saying that lead can't be weighed in units of 31.21gm (1oz troy)
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Depends... Weigh them both under the same system, and they'll weigh the same. Weigh the gold under its usual "troy" system, and the lead under its usual auvudipous (I bet a nickel I mangled the spelling beyond any hope) system, and they'll be substantially different.

As far as the original metric/decimal accuracy question... Measure it in metric, then convert it to inches, and you can bet on there being at least SOME error, no matter how many decimal places you take it to, since a "used" (as opposed to "The math says...") metric/inch conversion is always going to be an approximation. For quite a few, there's a "close enough" approximation - Think "half inch" and "13 millimeters" - They're not *EXACTLY* the same, but for purposes of wrenching on a bolt, they're close enough that the discrepancy doesn't matter. Get into a situation where there are enough digits to the right of the decimal, and suddenly you find out that the fit of the half inch wrench you're using on that 13mm bolt has *ALL KINDS* of slop to it, even if you can't "see" it in the "real world".

It's all about tolerances... For "wrench on bolt", 13mm/half inch is "close enough". But if you turn a part to 0.500 inch when the sheet specs 13.0000mm, or vice-versa, you may find that your 0.0500 inch part doesn't fit into the 13.000mm hole, or the 13.000mm part rattles around in the 0.500 inch hole like a BB in a boxcar when it's supposed to be a tight press-fit.

Personally, I think it's always best to work in *ONE* system if at all possible. Mixing measuring systems is a recipe for a crashed Mars lander

- As NASA so ably demonstrated a couple years back when they calibrated hardware in english, and wrote software in metric. (or was it the other way around? Either way, I think you get my point.)

(Hey, Gunner - I'm curious... WTF did this question have to do with misc.survivalism, other than perhaps inviting the whacko element that inhabits that group to cross-post into the machining/metalworking groups???)

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There are all sorts of folks on MS..the vast majority being of sound mind. All manner of topics are discussed, including machining, etc etc on occasion.

I dont see any nut cases (other than myself of course) from MS posting on this thread. Do you?

On the other hand..I recognize several that are of sound mind, some of which are machinists, or scientists.

Gunner

"If thy pride is sorely vexed when others disparage your offering, be as lamb's wool is to cold rain and the Gore-tex of Odin's raiment is to gullshit in the gale, for thy angst shall vex them not at all. Yea, they shall scorn thee all the more. Rejoice in sharing what you have to share without expectation of adoration, knowing that sharing your treasure does not diminish your treasure but enriches it."

- Onni 1:33

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Sorry, wrong answer. It was a nautical mile.

PDW

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I just machined a housing that the print was in metric... converted from inch. The pipe tap dimensions were in metric for the drill sizes and the pipe taps themselves were 1/4, 3/8, and 1/2 BSPT.

John

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I was taught recently, at trade school that there are 2 metric threads

- coarse and fine. The fine one is an uneasy compromise, so most tapping charts etc on the classroom wall had all the fine threads in a variety of imperial standards, depending on material and application..

Andrew VK3BFA.

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I'll call this bullshit. Metric thread designation does not have any decimal places for all the standard threads. For special fine threads (and this is definitely not the case here) two decimal places are only possible for something less then M10. For all the plumbing needs inch threads were used indeed. There was also no way that russian designer used some non-standard thread - it was just not possible.

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