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 Home Model Engine Machinist > Trying out metric

03-21-2017, 01:08 AM   #81
gweloboy

Join Date: Apr 2016
Location: Leesburg,GA
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Here is my bit of info. I went on a bolting course given a Swedish bloke about 10 years ago.
He recognized my accent as Rhodesian not South African.
He told us fine threads were an attempt to stop nuts coming loose before effective locking systems were developed.
He told us that no-one was doing any research on Inch bolts, all was being done on metric bolts.

I took some science classes at the local college and realized why metric struggles here. The compulsory Imperial/metric conversion lessons are seen as not much more than arithmetic/mathematics exercises. As a child overseas I remember the change to metric. At the beginning of the school year everything went metric -that's all you learned. All new machinery was metric. We learned to convert because all existing equipment was in Imperial. S.Africa went so far as to ban any Imperial measuring equipment - no metric/inch tapes etc allowed.

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03-21-2017, 05:01 AM   #82
Cogsy

Join Date: Jul 2012
Location: Perth, Western Australia
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I know it's a super old post from a super old thread but I had to laugh at Lew Merrick's comments about what the SI units were based on and how they "screwed up" the calculations. While it's true the definitions have been altered and refined, ever closer to a 'perfect' and repeatable quantity, they didn't "screw up" the calculations, it was just the best standard they could apply. Meanwhile, Lew doesn't mention the basis of the definition of an inch (width of an 'average' man's thumb) or foot (length of an 'average' man's foot) or yard (length of an 'average' man's belt), etc., etc. And what did they finally settle on to truly define the inch, foot, yard, pound, etc. - they are all now officially defined against the metric standard.

Oh, and the Mars lander (Mars Climate Orbiter) that was lost was due to a Lockheed-Martin failure where their equipment produced output in American customary units when the rest of the mission expected (and as they were contracted to provide) SI units. No "powers of 10" issue there.

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Al.
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03-25-2017, 11:15 AM   #83
rodw

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Cogsy, I'm on your side. Like you I live in Australia which converted to metric in 1966 with what is acknowledged as being the most successful metrification project ever ran. Like you I am old enough to remember the conversion and being taught how to do maths in imperial units in school. Wow! how good was it to work in litres instead of pints, quarts and gallons!

Yes I remember we got dragged kicking and screaming into the metric system but it all changed in 1978 when I started to study engineering at University. In semester 1 we had to purchase a little book called "SI units" that was filled with conversion factors and explanations of the more complex metric engineering units. About once every 5 years, I still pull it out to check to check something like the relationship between kPa and bars, but I've never referred to it for conversion factors for the last 30 years.

Like you, during those early days, my head became filled with useless conversion factors like 25.4, 3.28. 0.3048, 2.471, 2.204 and many others. But eventually I succumbed and banned imperial measurements from my life and can now use those brain cells for other purposes. I recall, how I could once work in fractions with ease, but now it is a distant memory. I have a set of AF sockets I bought way back in 1978 that have not been used for years....

The last conversions in my mind to fall were land areas (it was much cooler to say I grew up on a 100,000 acre property than one that was only 40,000 Ha). The other one was rainfall. 100 points was embedded much more deeply than anything else given my rural background where rainfall was so important as it was almost a religious experience to empty the rain gauge when it finally rained (25mm was soooo boring).

I am pleased you corrected the reasons for the loss of the Mars spaceship as the excuse offered also clashed with my memory of the incident. Lets face it. Every major engineering project in the world has used SI units for years and this project was bought undone by a team that did not use them.

The fact remains that only 3 countries in the world cling to the imperial system. One of them actually corrupted the base units so back in the day, I had a whole host of secondary conversion factors for US gallons vs real gallons.

I just did a bit of quick research on Google and it just so happens that of there are 7 billion people living on this planet. But those 3 countries represent just 5.38% of the worlds population.

Eventually, you guys in the US will succumb and you will finally acknowledge you are a very small minority group. You will embrace the global standard. Yes, there will be much gnashing of teeth and wringing of hands just like there was in Australia back in the 60's and 70's. But remember, you are a country of 318m people and billions of others have converted to metric and survived. Surely, such a small handful of people can also make the grade.
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RodW
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03-25-2017, 02:19 PM   #84
RonGinger

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I found a very interesting document by the NIST on metric in the Us. http://https://www.nist.gov/sites/de...tric/1136a.pdf

Looks like a lot of government purchasing is now in metric, but we still have the 'freedom' to use whatever we want, hence the mess of units.

03-26-2017, 02:12 AM   #85
Cogsy

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As SI units are the official 'language' of science, it's interesting to hear seminar talks from American scientists fluently, and intuitively, speaking in SI units. They were bought up using imperial for everything but their careers necessitated a change which they obviously underwent. I wonder what units they use in their 'everyday' lives, do they think of a summers' day in degrees c or f, meat in lbs or kg, milk in L or fl.oz? I'd guess whatever they're most comfortable with, which I further assume is metric. My parents were born, raised and working full-time for years before metrication but completely made the change long ago - except, as Rod says, they still live on acres of land.

Another edit: I read the paper Ron found and it was interesting, just a note though - mL is a volumetric measurement, for dry ingredients for a recipe (or even quantities in chemistry, etc.) we use mass measurements in grams. We only use mL or L for fluid or gaseous quantities.
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Al.
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03-26-2017, 06:23 AM   #86
rodw

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In my first year at university in 1978 when most of us worked in imperial units in everyday life, the lecturer calculated the power output by an engine in SI units and came up with the result in kW. It took half a blackboard.

He then redid the same sum in imperial units and came up with the same result in Horsepower which saw him fill 3 blackboards before announcing to the assembled students "And that's why in Australia we prefer SI units! It was a powerful incentive to get our head around the new SI units. I had never even heard the term SI units before.
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03-29-2017, 07:35 AM   #87
gunna

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Location: Melbourne, Oz
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I have always wondered at U.S. tv shows like CSI and Bones which routinely quote metric units for distance and weight. I thought they were just trying to be "scientific".
Ian.
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03-29-2017, 12:52 PM   #88
ShopShoe
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In interacting with my own doctors and taking my mother to hers, It's mostly metric: Doctor tells me the size of things in mm and tells me to drink 3 litres of water a day. Docter tells Mom to gain 10 lbs and drink 10 8-oz. glasses of water.

My wife is a nurse and we tend to use units interchangeably without problems.

In addition to a fondness for metric units, our personal inclination is to use 24-hour time: Every clock we have that allows it is set to do so. I was never in the military, but I think it makes more sense.

--ShopShoe

03-29-2017, 01:06 PM   #89
blighty

Join Date: May 2011
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had a mate years ago, when we were kids building a fort, tree house, go cart etc. he would say cut this off at 3feet 1 inch and 5mm. as long as i cut it at 3feet 1 inch and 5mm it would fit. if you look at a tape measure with inch/mm, it makes sense.

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05-17-2017, 08:45 PM   #90
Rig30mechanic

Join Date: Oct 2013
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Better with metrics.

I was educated in a time when Australia changed from Imperial to Metrics and have worked in engineering for the past 47 years. Many of these years were on oil rigs both on land and offshore.
The idea of measuring distances by using fractions of a dead Kings smelly foot is difficult to understand when we have available a simple system based on the number of fingers on a standard person.
To be able to add in 10's is pretty easy.
I have even had to work with "oilfield" tapes where the feet" were divided into tenths to make addition and notation easier. It would have been easier to use metrics.
Congratulations on seeing the light.

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