Boeing and metrcication question

On Tue, 18 Sep 2007 17:16:33 -0400, "Michael A. Terrell"


No, that third world, union run country that still has it's royal family. Gerry :-)} London, Canada
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Ed, thanks for the insight. I do agree that most machining can be done in inches and decimal parts thereof. However, at some point you still have to reach for a drill and get involved with fractions and letter designations. That part of the process could use some improvement. Why don't they simply make/package drills in decimal inches?
Ivan Vegvary
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Actually, they do, if you're buying in quantity and you buy from somebody who supplies volume manufacturers. But the answer to your question is that it's one of those old traditions that are hard to break.
-- Ed Huntress
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Ivan Vegvary wrote:

Your drill indexes and wall charts do not list decimal sizes?
The three indexes in my tool box, all have the decimal equivalent on them. The wall chart I use most, has a list of all the "normal" drills in decimal inch, as well as decimal mm from smallest to largest, showing the sequence of sizes, of normally stocked drills in the 4 systems that we use (number, letter fraction, metric).
I am pretty sure we could shitcan the whole thing, if we just stocked the metric sizes in tenths all the way up to, say 25mm, but there would be a lot that never got used, eh!
Cheers Trevor Jones
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Thanks Trevor, I have all the charts and indexes. Since a 64th is approximately 15 thou why don't we simply label drills in increments of either ten thousandths or 15 thousandths. It would eliminate all of the charts.
Ivan Vegvary
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Ivan Vegvary wrote:

We could, and then we would need charts and indexes that told us which one was the one that matched up with the required hole size, esp when dealing with legacy standards. That would also leave out a pile of sizes that would not fit nicely into the spacing, sorta like why we have number and letter sizes, instead of just 64ths or 128ths fractional sets.
Making a law that "Thou sall be Metric henceforth!!) did not change any of the stuff that was already in place. Houses built to inch dimensions will be around for a while yet. The land survey of Canada (at least the prairies) is laid out in neat 1 mile by 2 mile grids. Etcetera, etcetera, ad nauseum. (my latin for the day!:-))
Canada tried that. Metric by decree. Then they found that, in order to be of any use at all, civil engineers, for example, had to be able to read the drawings that were done 100 or so years back, and make sense of them, so they started teaching both systems again. I can buy a yardstick, if I want to!!
If I get the ghist of it right, that was the intent of the metric system in the first place, to reduce the number of systems in use. It just added another.
Cheers Trevor Jones
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wrote:

the intent was to base the systems on interrelated values rather than arbitrary values with conversion factors between them.
a litre of water is a thousand cc's and weighs a kilo.
as opposed to 23 and a half kilderkirkins weighing 2 cwt 56 lbs 31 ounces in king james footric measures. :-) ....sorta thing
I do most of my work with a vernier marked out in mm and in 128ths of an inch. it is wonderful and direct. whichever system gives me fractionless numbers gets the nod.
Stealth Pilot
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How do you get "fractionless numbers" in inch, when your vernier is marked in fractions? I don't get it.
As for the arbitrary units, I don't know of any that actually involve conversions in practical use. The units in practical use generally have whole-number relationships.
And beyond the largely illusory advantages of metrics in dimensional measurement, the supposed advantages of metrics' "interrelatedness" break down. Units of force, for example: the Newton equals roughly 0.101 972 kilograms of force (kgf). The cussedness of natural phenomena (defining a unit in terms of acceleration, for example, when its common use is as a measure of force) gets in the way of numerical elegance. Note the "roughly." Also note the lengthy decimal. There are many other such examples.
I'm not suggesting that the metric system is in any way "inferior." I'm just pointing out that its supposed advantages are vastly overblown.
-- Ed Huntress
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Ed Huntress wrote:

There is no such thing as "kgf". Outdated since decades and no longer "legal".

It's no wonder. The gramm is a unit of mass. Period. Never was different. It certainly is inelegant when used as force. The only thing getting in the way is an unknowing user. :-))
Nick
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Pffft. That wasn't the point. The micron isn't "legal," under the SI either, but everybody uses it, because "micrometer" can be ambiguous, since it's also the name of an instrument. Neither are the calorie, torr, gauss, maxwell, or oersted "legal," but they're all widely used in different sciences.
The point is that the standard units don't necessarily relate *in whole numbers* to the things we actually measure. Trying to be neat and tidy, metrics sometimes shoots itself in its own foot.

Nonsense. The Newton is defined in terms of kilograms, as well. It's just that it's defined in terms of acceleration rather than as force itself.
You sound like one of those pro-metrics folks who make up all of this supposed neatness of the metric system, Nick, and then wonder how everyone else doesn't agree with you. Those of us who don't agree with you are the ones who actually have used those units. They aren't all that neat.
-- Ed Huntress
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Ed Huntress wrote:

The "problem" is the acceleration on earth (depending on *where* you measure it). It is 9.81m/s^2. Thus the factor of 0.1... to "convert" (it is *no* conversion) mass to force. F = m * a
Maybe you find a planet where a = 10 m/s^2. :-)

You didn't understand the SI-system. It is based on **as** **few** **as** **possible** units, the rest is derived/partially defined by them. They are: kg, s, K

I don't wonder of anybody who doesn't agree but at the same time doesn't understand the difference between mass and force.
I only have to look at the domain-dependant units of pound, pondal, pound force and whatever to see what mess it is.
Read about the SI-system before you talk about it.
Nick
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There probably is no such planet, which makes my point. The natural world and natural phenomena do not succumb to attempts to make "rationalized" multi-dimensional systems of measurement, most particularly systems that try to build everything from a minimum (seven, in the case of the SI) number of base units, which are themselves derived from only three fundamental units.
It works great in theory and doubtless it's an aid to many scientists working in many fields. For others, including the field of medicine, where I've been writing for the past few years, it simply results in a lot of clumsy derived units. Thus, you'll see older CGS units mixed with SI units in many fields, as a simple matter of practicality.

Yes, from which the base units of the metre, the kilogram, the second, the ampere, the kelvin, the mole, and the candela are defined. And then dozens of other units are derived.
It's a theoretically elegent system. By using those base units, the SI committee has developed a system that is theoretically coherent and conceptually minimalist, but which also forces you to keep things in your head that are far abstracted from what you're actually measuring, or to memorize the system without thought -- which obviates any "rational" advantage the system may have, in much practical use.
Again, we're not arguing over the advantages of the SI system to a scientist performing elaborate calculations about celestial bodies and their photometric properties, or remotely measuring their mass and angular velocity. We're talking about the everyday measurements that make up the vast majority of numerical evaluations made by people in the world. For them, defining the unit of force in terms of acceleration, when they're interested in how big they'll have to make a support to keep a cistern off the ground, forces them to use (if they're using SI units), abstractions that they'll have to memorize or convert roughly into something sensible -- the weight of that cistern when it's full of water. They're forced to use Newtons, when what they're dealing with is kilograms of force, or pounds, if they're so inclined.

I understand it quite well, thank you very much. The traditional units of force have been defined quite precisely in terms that are perfectly acceptable to the stickiest proponent of the SI. The latter just don't like those derived units. They're inelegant. They're also very useful.

I don't know anyone who uses pondals, and the pound, both as a unit of force and as a unit of mass, is quite handy within its domain.
I am not domain-independent. I am not trying to write the General Theory of Relativity. Neither are you, and neither is (almost) anyone else.

You really can be annoying at times, Nick. It's very unlikely that you've read as much about the SI system as I have, unless you spent more than a year, as I did, outlining a book on quality assurance.
-- Ed Huntress
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wrote:

<snippage of noise and opinions :-)>
Ed:- I will be using Imperial measure until I die. Damnit, I will use Whitworth and BSF threads in preference to others until I no longer have the capability to make them. But.. The SI system holds together far better than the Imperial system for anything that involves any form of calculation. I have no problem with a 1 hp motor, but going from there to 550ftlb/S and 2,545Btu/hr as opposed to a 1kW motor being 1000Nm/S and 1000J/S brings it home that the SI system is _rational_
Other derived units:- 1F=1V/C=1Vs/A What's a Jar worth? 1Tesla=1W/m^2=1Vs/m^2 , I don't even know if there is an Imperial unit of magnetic flux density!
The conversion factor between base and derived units is always 1, PI or E. That really helps when checking a calculation for consistency. You _can_ do the same with fps units, but only if you stick to base units. This isn't abstract science, this is everyday engineering, Things like calculating the impedance of a length of power line, or the size of the flywheel needed on a press.
<DEVIL'S ADVOCATE> The SI system will entirely replace the Imperial system and pretty much has done in all of the world except for the USA and some scattered romantic holdouts in the rest of the world. In 30-40 years time when the (federal) EU, China and India all have larger economies than the USA, what will be the advantage of using a measurement system that the rest of the world thinks is mediaeval? </DEVIL'S ADVOCATE>
Mark Rand RTFM
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That's fine if you're doing calculations involving joules and motor output, Mark. But for every design engineer doing conversions there are ten people who have to figure things such as, say, how much of the 500-kg load they just put in their trailer should be shifted so that roughly 10% of the load is on the tongue. Do you seriously think they should convert the load to Newtons, and then gauge the tongue weight by estimating it in Newtons? I don't think so.
My point is that the traditional, non-SI units more often are based on measures that relate to our senses, without conversion. Even if they result in inelegant units, they often are more practical for ordinary measurements.
Even where metrics stand up well in those every-day measurements, the SI usually has little or no advantage. Sometimes, like with tongue weights and converting kilgrams of force to Newtons and back, the SI results in a confounding complication.
Again, on the whole, I wouldn't claim that the inch, or Imperial, or CGS metric systems are superior to the SI. I'm just saying that the supposed advantages of the SI don't apply in practical uses by most people, and that sometimes they can actually be a disadvantage.

Not many people would care, either. d8-)

You're talking about design engineering. We started this discussion talking about manufacturing, where it matters little, and I've tried to point out that most people who measure things are interested in neither scientific nor engineering calculations. I also have mentioned that, where metrics are preferred, we use metrics in the US. We even use the freakin' froggie SI. d8-)
Virtually all of our scientific calculations are done in metrics. Like scientists in various specialties everywhere, we don't always prefer the SI to CGS. Medical science still uses calories, for example, pretty much worldwide.
None of this has had an influence on our exports or imports. Nor has it seemed to retard our capabilities to invent and innovate. So, what is your point, in the end?

Well, the news here last week reported that the EU has decided to let your pubs continue to use the pint measure. I didn't realize the EU had that authority, but it was damned sporting of them, don't you think? d8-)
Perhaps they read Huxley's _Brave New World_, which addresses this very issue.
-- Ed Huntress
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Ed Huntress wrote:

No, the point is different. You have to distinguish between force and mass. For some simple minded people (pun intended or not?) it is the same, but it ain't.

It works even greater in practice!

Have no insight into medicine at all.

The coherent system (why do you always say "theoretical", it *is* coherent) has a lot of advantages as soon as you start to make calculations.
A simple and cyclic example: Your did some math and the result's unit is [kg * m / s^2] Now what's that? It is force, so the unit is [N]. And how do you know? By the formula f = m * a. If you do the check with units it is: [N] = [kg] * [m/s^2]
That system is really great as soon as your calculations are a single step behind adding. Do a check with the units and you see whether you made some nonsense or not.
If you do have a problem "converting" mass to force, simply multiply the kg by 10 and you do have Newton.

Are you supposing to do the calculations in SI and then convert them to imperial? Don't ask for the famous prove what the result is.

Hmm ... I mean is someone is failing to understand the difference between mass and force and isn't able to calculate the resulting force, will he be able to properly dimension the legs (Euler's buckling resistance)? I bet no. Or the other way round: Does it help Joe Bar in calculating the stress of some odd-shaped column when he is using odd units? As soon as that Joe Bar wants to find out whether a screw is strong enough to keep his trailer together, it doesn't help to work in pounds when he considers the torque the screw is tightend with and the resulting stress and clamping forces (that was a longish German sentence :-))

I remember a discussion about a year ago. It was such a mess that I had to bail out. And again "he pound, both as a unit of force and as a unit of mass, is quite handy" is just quite confusing and will only result in errors.

Yes, I can! ;-)

So, I do have to be annoying again: | Units of force, for example: the Newton equals roughly 0.101 972 | kilograms of force (kgf). That's what you wrote!
I have several answers: a) There is no such thing like kgf b) did you mean kp? c) kp was left behind 1960 and replaced with N e) from the factor 0.101972 I see that we live on the same planet (1 / 0.101972 = 9.806..) but I doubt that this is true everywhere. f) from e) I feel that you didn't fully understand the difference between force and mass.
Sorry! I do *not* want to kick your ass, I'm just a bit pi**ed when people are confusing things. And I see it so many times here that people write MM when they meant mm (what would MegaMega mean?) or write S when they meant s (I don't know what Siemens (the inverse of Ohm) has to do with time) etc.
But!!!: If you reduce the discussion to inch vs. metre (or meter) it is not worth continuing. There is just a factor to convert between them. Neither meter nor inch is more precise. The discussion starts when you look around and see things like feet, AWG, steel gage for sheet metal, drills by numbers and letters, etc. No such thing in the metric system.
Nick
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I mean coherent according to physical theory, rather than to sense experience. It's based on theories of fundamental physics rather than the kinds of things we see and feel when we do most of our measuring in life.
And yes, if you're involved particularly in design work involving more than diminsional measurement and you're doing calculations, it's a neat system -- particularly if you have enough knowledge of physics to be comfortable with the derived and multi-dimensional units. For the rest of the world, the advantages, if any, are slim or nonexistent.

Most people don't do the math. If they do, in the US or anywhere else, they're probably using metric units and possibly SI units.

Don't forget to double-check your decimal places. If people would stop using that damned centimeter they'd have far fewer errors of that type. d8-)

Arghh! I thought you were arguing for accuracy. Ten N does not equal a kg of force. 9.80665 N equals a kg of force (by gravity, at the earth's surface at the equator, anyway, which sure beats the hell out of the accuracy you get when you "multiply the kg by 10"). It's one of those nice, neat, whole-number relationships in the metric system, so useful when rocket designers are calculating thrust-to-mass ratio. <g>

What famous proof? And what "result"? Most current "Imperial" measurements are defined in terms of metric units.

Tell me, does the average consumer who weighs his kilogram of potatoes keep in mind that he's actually measuring force, and that he's not actually getting a kilogram of potatoes unless he's using a beam- or pan-balance? Do they not use springs in the scales at grocery stores in Europe? Even if he knows Newtons, is he fully aware of the difference between mass and force? I bet no.

If Joe Bar is calculating the Euler's buckling resistance of columns, he is not part of this discussion.

It can, if you're being fussy. But the errors are nothing like the ones you get when you say to multiply the number of kilograms by 10 to get Newtons.
Nick, I wish I could summarize my points on this sufficiently to clear up all of the arguments. It may surprise you to know that a big bottle of Coke in the US is a 2-liter or 3-liter bottle. It is not a 2-quart bottle. Furthermore, the engine in a Ford or Chevy is not identified on the trunk as a 183 cubic inch engine; it's a 3-liter engine. Despite this we don't encounter enough problems involving, say, the speed of light and the mass of a banana to have much trouble with the dual system.
And so on. The US is not hidebound to the Imperial system. We just use it as a matter of economic good sense. Given the economic filtering process that free-market economics puts us through, you can be sure we'd be 100% metric if it truly was an advantage. We're much better at that than any country in Europe has been, although you do seem to be coming around to a fuller appreciation of the useful power of markets.
And the people doing complex calculations with force, acceleration, and so on are using metrics with few exceptions. As for the SI, it's a mixed bag, in the US as well as in the rest of the world. There are a lot of holdouts for CGS (usually expressed as "cgs," but who's editing...) everywhere in the world.
-- Ed Huntress
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At Standard Temperature and Pressure STP only. Water changes if not on the mark.
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
Stealth Pilot wrote:

-
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Ivan Vegvary wrote:

Tradition and tolerance buildup.
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Ivan Vegvary wrote: . Why don't they simply

Mostly, they do. All of my drill index boxes have the decimal inch size listed right by the size "designator". I have number, letter and fraction series drills, but the fractions are basically just another "size designator", like #43, or letter M. I work by the decimal inch size.
Jon
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For myself, I calculate in metric in Physics and Engineering. In the home shop I use drills from my sets of wire 80-1, Letters, Fractions to 1/64 and metrics by .1mm through 25mm or 30 - been a while since I was in that box. I use all of them - have charts that list all of them in order. When I want to drill slightly larger or smaller - it is from the total list.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
Ivan Vegvary wrote:

-
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