Metric vs Imperial or vice versa

[rake60]

Well Marv I do know one answer off hand.

A shot gun gauge was determined my the number of lead balls the diameter of the
bore that it would take to make 1 pound.

The rest of them I'd have to look up.
I've never run into any of them in my home or work machine shops, but it's
still interesting reading.

Rick

 

[Bernd]

The place I used to work built gear cutting machines for the world car makers. Had to work in both imperial and metric. The hard part was the "metric angles". They threw me for a loop.

Prefer to work in imperial since all stock is available in imperial sizes. If, and this is a BIG "if", I build Bog's twin piston steam engine I'll have to give metric a try since it's all dimensioned in metric.

Oh and the other thing that was tough was the electric. 60 cycle imperial and 50 cycle metric. :

Bernd

 

[Bogstandard]

I am learning a lot here about the way the US system works.

How I understand it now.

The layman in the street has great difficulty because of the fraction system, never having been subjected to the 'other' side of the imperial system of thousandths (millies as I think you call them). If it comes to more than how many fingers and toes, they are out of it.

The engineering side works in both fractions and decimal imperial. So basically the tech minded are working in a basic metric system to begin with, so can swap over easily to full metrication. They understand the metric system, so maybe the stumbling block is the direct conversion between the two different sizes.

--------------------------------------------------------------------------------------

So I will explain how I do the basics, and you can elaborate on my methods.

For rough guesstimations I use the standard -

1" equals 25.4mm and 1mm equals 40 thou (0.040"), and vice versa.
So 0.1" = 2.54mm and 10mm = 0.40", slightly out but it gets me near enough.

I find that this gets me within striking tolerances of what I am doing, and can easily be done mentally.

If I want to go to much tighter tolerances, I then refer to my little pocket bible.

So I don't have to use a supercomputer of a brain to get to where I am going.

I just remember three things, the two calculations above, and where the hell I left my little book.

So to summerise, I can get near enough with what I have got in my head, with a little bit of extra maths, and to reach final size, twiddle the knobs on the machinery, and measure it.

I could at one time convert large numbers either way in my head to within a thou of where I should be. Now that one of my two brain cells has gone missing, I find that the above is all that I require.

It might seem that I have over simplified things, not true, this is all that is required for getting the job done in what we are doing here.

Now about deg F to deg C. I multiply deg C by 2 and add 29. The other way around, subtract 29 from deg F and divide by 2. If you need it closer than this, you are in the wrong business.

Just like the piece of string for a weather forecast.

Hold it between your thumb and forefinger.

If it is swinging side to side, it is windy.
If there is water dripping from the end, it is raining.
If you can turn your hand the other way up and the string stands up straight, it is freezing.

Don't make life more complicated than what it is.

Do you have any little conversion factors that you use to get the job done?

John

 

[Bernd]

Bogs,

When I worked in the electrical department at work we made up cables for the machines in metric length's. We had an elderly gentlemen who could not do the metrics. He tried to convert the lengths in to feet and inches. He had a very hard time using a metric measuring tape. I finally told him if I gave him a rope with knots in it and told him to cut a length of cable that was 10 knots long, could he do it. He said he could. So I told him not to worry about converting and just to use the metric tape measure and think of it as so many knots in a rope. He had no problems after that.

Some times a simple solution works. I know I have a hard time visualizing 1 kilometer. But if I convert it to .6 miles I can then visualize the distance. It's just that I was raised on the imperial length and can visualize that unit better than metrics. I can work with either if necessary.

Bernd

 

[compound driver 2]

Hi
My big objection to metric is being told by the government I have to use it in work.
I run my own machine shop, I take in work thats as a rule steam related and for engines
coming close to 100 years old.
Why would i even want to convert everything to metric? I dont have the spare hours in the day to do
it or want to do it.
Working with fractions is as easy as reading a book or eating a sandwich. Once you grasp that 1/32 of an inch is .03125 and 1/8th of an inch is .125 how can you go wrong? Adding fractions was taught to me in school and still comes as easy as it did 40 years ago. Surely kids must still be taught how to add and subtract fractions. No one can tell me fractions have been dropped from education my boys learning them now.

We built an empire on feet and inches why let it go at the whim of a politician in europe.

Cheers Kevin

 

[mklotz]

My set of questions was designed to highlight the sort of problems one encounters when using a hodgepodge like Imperial and to do this without getting into a lot of numerical computations. It was also meant to show that the difficulties with Imperial extend far beyond the simplistic linear measurements we encounter in the amateur shop. Lots of Imperial boosters claim they don't want to switch because they already understand the Imperial system. If that were true, answering the questions should be easy, especially so for anyone calling himself a model engineer.

Rick's answer to Q1 is correct - 12 gauge refers to the number of balls to a pound.
Now, isn't that a sensible way to denote something? The logical measure is diameter (ball OD or barrel ID) and the means to measure such certainly existed if shotguns were being manufactured but no, let's calibrate the gun according to some obscure tradesman's (the lead caster) measure of convenience. If I developed a new type of super drill and decided to label them with a number that represented how many of them it took to make a pound of weight, wouldn't you think me nuts?

Another question I should have added to the list is:

If Imperial fractions (1/4, 5/16, etc.) are so useful, why aren't micrometers graduated in 1024ths of an inch?

Bernd,

What do you mean by metric angles? Some of the Europeans (French particularly) use the 'grad' (90 deg = 100 grad) but, AFAIK, that's never been incorporated into the metric system.

 

[gilessim]

A couple of things here, I may be wrong but I was always told that 12 guage was the diameter of one ball of lead weighing 1/12 of a pound. A pint of water in the UK was said to weigh 1 1/4 pounds x 8 pints =1 gallon =10 pounds, I don't know how accurate that is and I Know that US gallons are smaller but I've always found it curious that linear imperial measurements are quite close to imperial weight standards. Also as Marv points out, dividing an inch into 1000ths was a step towards decimalization, how big a fraction can we cope with? .One more spanner (or wrench!) in the works here is that 1cc of water ,was discovered recently, to weigh slightly less than 1gram ,so that poor physics students in Europe now have to make complicated calculations to compensate!

I have two questions in one here, following on Marvs theme; What is the origin if the inch? and how was the length of a meter determined?.

BTW being a Brit ,I won't say that a hundredweight is 112lbs, but in question 7 ,I don't think any of those are imperial except perhaps, Point and I think that comes from compass divisions, 1 point being approx 1/72".

Giles

 

[mklotz]

A milliliter of water weighs exactly a gram only at 4 degC, the temperature at which water is most dense. For critical chemistry purposes, one must use a temperature compensation at any other temperature. The total effect, though, at any temperature where water can exist as a liquid, is miniscule.

 

[zeusrekning]

Lots of Imperial boosters claim they don't want to switch because they already understand the Imperial system. If that were true, answering the questions should be easy, especially so for anyone calling himself a model engineer.

I just lost my whole post :'(.

Marv, I think you could come up with ten similar questions relating to the metric system. I don't see how questions 1,2,4,6,&7 relate to what we do. I forgot half the $#!& I wrote. I can barely remember that there is 11-1/2" in a foot. Much less how many pounds a British CWT weighs. I think a good machinist should be familiar with metric and imperial. A lot less familiar with imperial if in a country that does not use it compared to how familiar an American should be with the metric system.
I expect the people I buy material from at work to be fluent in there knowledge of materials. I do not expect them to be able to recite ASTM matl codes. I have some salesmen that can. It impresses me as does your knowledge of math Marv. But as long as that salesperson can know where to get the information I need
I am satisfied.
There are a lot of members here who came into this hobby with no experience at all in machining and probably some with almost know knowledge of math or measures beyond basic day to day math. Marv's day to day math is different than mine and mine is different than an electrical engineers. Like I said a good machinist needs knowledge of both systems. A better machinist needs to know where to find the information they need with out filling that fileing cabinet in there head with to much info that won't be used. When the time comes to need to know what a Jeroboam is Google it and have some where to put it where it can be pulled up if needed again. I have no problem making parts to a metric print. I am sticky when converting surface finishes to metric. But a lot of these guys are spending what little free time they have trying to learn maching without trying to learn a new measuring language. If you do not know either, learn metric first. Metric is a better system. But unfortunately most of the time there is no choice. I am sure a British machinist is not going to be a better machinist b/c he uses metric than an American using imperial. Oooh, That's an argument I'm not touching :big:
BTW, A meter is the distance light travels in a vacuum in 1/299792458th of a second. I did not know that but
I googled it. I'm sure my whole life I will never need to know that but if I ever do GOOGLE.
To wrap it up , Metric is a better system there is no argument there. If you can't seem to get it, convert when needed and you will get by no problem. If you are stuck there is help here. I wish my English was better so my post didn't sound so ignorant but I try and get by. There is another example look at the language we all use and the flaws in it and how hard it is to understand. It is still the worlds most used language.
Tim

 

[mklotz]

Tim,

This is no longer a discussion of what system a guy working in his basement shop should use. We've already answered that and the answer was, "whatever is simplest for him and most economical given where he lives." John, the OP, solicited our views on the two systems and, unfortunately, I have some very strong views based on many years of having to deal with both systems.

What I'm trying to convey is that the Imperial system is a complete system of units, not just the linear measures we use in the shop. Furthermore, that system is badly flawed, full of doubly-defined and confusing measures. It's existence and the confusion it's caused have already cost us the loss of two multi-million dollar spacecraft and a number of human lives in air crashes. The longer we keep it alive, the more mistakes, minor and major, are going to be made. Obviously, metric will not eliminate mistakes, but, given an ever dumber population, it will go a long way to reducing the number.

There's more to life than engine-building and intelligent folks like those here should understand more than just what they need to do their immediate task. The key to a long life is to keep learning.

Lots of folks (Americans especially) have made the case that Imperial is as good as or even better than metric. I'm trying to point out that they're saying that without fully understanding just how screwed up the Imperial system is. Perhaps if they understand that they'll come to appreciate that the advantages of metric are far more than the powers-of-ten thing that's always dragged out in these discussions.

The Imperial system could be fixed. Trouble is, to do that right, you'd need to introduce most of the *system* corrections that have already been formalized in the metric system. Since the system has already been worked out (and is used by most of the world - the USA and Mynamar (Burma) are the only countries who haven't adopted it), why not use what's already there?

Finally, let me point out that I do most of my shop work in Imperial - mainly because I live in the USA and that's the most economical way to go. I use metric only when working to a metric print or doing something that will never have to interface with anything Imperial. I'm not sitting in some (metric) scientific laboratory pontificating on what shade-tree mechanics should do. The reason I despise Imperial so much is because I'm forced by circumstance to use it on a daily basis.

 

[Bernd]

Bernd,

What do you mean by metric angles? Some of the Europeans (French particularly) use the 'grad' (90 deg = 100 grad) but, AFAIK, that's never been incorporated into the metric system.

Was being a smart a$$ Marv. I wanted to see if anybody was actually comprehending what they were reading. I know I've done it. Read something and then went, What? Usually I can catch somebody.

And I couldn't answer any of your questions. Interesting to know they are Imperial. I did learn one thing. The gauge of a shot gun. Very interesting.

Bernd

 

[shred]

The trick with the odd imperial measurements and the reason they hang around is they were all homegrown and thus originally meant something to somebody-- to an old lead-shot-caster, 12-gauge is far more meaningful than ".731" or "18.6mm" or 47/64", so they invented 'gauges' instead of using inches or furlongs or split-hairs, which they no doubt already had. It made their lives easier since they were already whacking up pounds of lead in various fractions to make balls out of them.

The trouble is when people that didn't invent the unit want to use it for a different purpose, or worse yet, compare it to something else entirely. That's where the troubles start and other people's lives get more difficult. To the shotgun barrel-maker, the number of balls-per-pound-of-lead is a lot less interesting than what diameter they have to make the pipe.

But.. as a friend said today.. if metric is so good, why don't we use metric time?

The average man-on-the-street will have a far easier time approximating half of something than a tenth or any other fraction of it... thus the roots of the fractional system. Take half, then half that, then half that...

 

[mklotz]

The trouble is when people that didn't invent the unit want to use it for a different purpose, or worse yet, compare it to something else entirely. That's where the troubles start and other people's lives get more difficult. To the shotgun barrel-maker, the number of balls-per-pound-of-lead is a lot less interesting than what diameter they have to make the pipe.

Exactly, Shred. The Imperial system has had several centuries to mature. Why do they continue to use measures (and there are many of them) that are irrelevant and awkward? A huge reform was in order and the French made that reform.

Incidentally, the French tried 'metric' time. They divided the day into ten 'hours' of 100 'minutes' each IIRC. It was a colossal flop and never caught on.

A very small number of clocks were built to this standard. If you ever run across one, buy it at any price. They're worth a fortune on the antique market.

 

[gilessim]

I perhaps misunderstood the questions here, as the imperial system was originally a set of standards that the Brits who hated the French at the time, decided on .I wasn't aware that French measurements were included later!

BTW the metre was determined in the 1790s I think(by the French!) to be a 10,000,000th part of a meridian from the north pole to the equator.

P.S. I didn't notice sack there! thats definitely English; 1 sack= 364lbs.

Giles

 

[Bogstandard]

The imperial measurements that are used in the US today, are in fact all the old measurements that the English brought across with them when they first turned it into a colony. It was later modified over the years to suit the colonists as they saw fit. Later in the 1800's, the US and English measurements were further split, when England finalised on its standard Imperial system, leaving the American English standards system to be enjoyed and modified as it suited the American people.

Most of the original and later Imperial measurements can be found here, and a bit of history how they both evolved.

http://en.wikipedia.org/wiki/Imperial_units

If you go to all the links in this URL you will find almost everything you need to know about the Imperial, US English standards and metric.

It also states that the US populace, calling it by the Imperial system, are in fact incorrect to be doing so.

Maybe on here we should be differentiating between the two English systems.
But to me totally unnecessary.

John

 

[Circlip]

The two old favourites always guaranteed to generate debate, Metric V Imperial and Carbide V HSS, :big: Nice one John. Back in the early sixties when I was partly forced to become bisexual in the textile machinery manufacturing industry, note I said PARTLY, one of the younger lads in the DO who had just bought a new set of drawing instruments was REALLY pi**ed off when we told him he would have to get a new set of Metric ones : Why partly? With the exception of one machine, the latest design, all the others were made in the brick s**thouse design era of steam technology and the British textile manufacturing owners were famous for their FRUGALITY. Not only that, but due to the quality of the machinery we made, we were supplying spares for some of the machines made in the early 1900's. Many years later, when employed in the Electronics industry, the PCB panels were deigned and manufactured to Metric dimensions but the coordinates for the press tools for punching the component mounting holes although given as Metric sizes were DIRECT Metric conversions of Imperial dimensions. Silicon Valley still made IC's etc at 0.1" pitching, so having to think in conversion dimensions bilaterally became the norm. I work in Metric cos that's what the dials on my Lathe/Miller are marked in, but there are still times when I think "Oh yes 0.1MM is four thou" Having said that, there are times when I think "Twelve and a half P - Oh yes, half a crown" Ian.

 

[Loose nut]

Lots of Imperial boosters claim they don't want to switch because they already understand the Imperial system. If that were true, answering the questions should be easy, especially so for anyone calling himself a model engineer.

Marv you have to look at your argument from a real world point of view, most people who use the imperial system do understand it, the IT being the part of it they use everyday which is simple measurement and weather temp. Cooks know what a teaspoon or tablespoon is and machinist's can measure using the inch etc. and that's what matters. All the other imperial measures don't really matter because we don't use them. The people who do use them are the only ones who have to worry about it.

Most people who use metric don't understand any more of the metric system than the same simple measurements and weather temp. because they don't use any more of the metric system than we use of the imperial system.

There are many people in metric countries that still use the imperial and other obsolete metric measurements because SI doesn't satisfy there needs.

P.S. how are shotgun bores measured in metric measurement IE" 12 guage = what?

"How many barrels definitions are there" there is only one that matters, a barrel of oil, which I believe currently is 35 US gallons, but this is subject to chance as it is an economic measurement more so than volume measurement. If OPEC wants more money they just lower the number of gallons in a barrel.

 

[Rog02]

Sirs:

Having worked in many locations around the world, I understand it is my responsibility to understand the measurement system that is to be used for the job. Arguing continuously which is THE best system in an exercise in futility. Any hack, shade tree mechanic with any experience in their tool box will tell you that.

Over the past 4 decades I have spent enough money with Snap-On dealers to put several of their offspring through medical school. I now can claim to own a fairly complete set of SAE, metric, weatherhead, whitworth, and AN wrenches and hand tools. My little fab shop is outfitted with both metric and SAE measuring equipment. The expense to me has been staggering. The options, are however not favorable to me. Failure to purchase the needed tools and acquire the knowledge to work to the required standards would leave me the option of flipping burgers at a fast food joint or becoming a teacher. I think, I will continue to buy the tools.

The metric system is inherently flawed from it's inception, that is a known fact. The "Imperial" system has undergone so many variations and adaptations to fit whatever trade or taxation issue, that it has become over bloated. Simply put, gentlemen, there is no truly accurate or perfect standard of measurement. As technology advances, the problem is expanding as new measurements are required for units of measure never foreseen. Anyone care to hazard a guess as to the definition of a MICKEY?

If you want to have some fun, try popping a beer (US), pouring a pint(UK), or cracking a stubby(Aus) and spend some time reading through this site.
http://www.sizes.com/units/index.htm
Be thankful we only need to argue converting "Imperial/Metric". :big:

Now I have to go feed my 1 stone tomcat and his 1/2 stone sister their daily 1/2 troy pound ration of cat food before I head out to the store to pick up a wine gallon of milk and 476 grams of butter.

 

[mklotz]

The metric system is inherently flawed from it's inception, that is a known fact.

Bold statement. Can you explain what you mean?

 

[doubleboost]

Hi
Living in England and being the wrong side of 40 i was tought both the imperial and metric system,
I still use both today (sometimes mixed up).
At work today i asked a 17 year old to take a 16th of the end of a bolt he just looked at me with a blank expression , he really had no idea what i was talking about ,2 mill however made all the sense in the world.
I think it is very sad that we are loosing imperial measurments
John