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Metric vs Imperial - Practical or Traditional?

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Paul Atkin17/08/2009 03:18:36
7 forum posts
I served my apprenticeship in the UK back in the late 1970's / early 80's and at engineering college we studied on a combination of metric and imperial machine tools - but only because they had a lot of older machines that had been donated.  Unfortunately my career took me away from hands on work and since then I have worked overseas in engineering where 100% metric dimensioning is used except in pipe threads.
I recently acquired a small hobby lathe from a very good friend which I shall soon be using with my hobby of Radio Control helicopters and planes so my interest on reading up what my new toy could do led to a study of what is happening on the internet.
I must say that I was shocked that to find that even though over 30 years have passed, so many people still seem to be working in non metric terms.  I even found this at a major supplier such as RDG Tools - many of their products are only listed in inch sizes.
For me, returning to a world of inches and thousandths is too horrible to contemplate, I don't own any imperial drills or taps / dies.  I can no longervisualize what 5/16" looks like for example.
So my question is, why are inches still so popular for model engineers? 
- Is it for some practical reason of sizing and scaling? 
- Is it that our American cousins refuse to change their ways? 
- Or is it that many of the people writing articles are of the pre-metric generation and are still more comfortable thinking in traditional terms?
JasonB17/08/2009 07:33:02
16922 forum posts
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-Practicality - I don't think it is any harder or easier to work in metric or imperial but do prefer imperial dims in decimals. Its obviously more practical to work in what your machines are callibrated in but with the increased use of DROs this is not a problem.
-USA - Most of the steam related models do not originate in teh US so its not that but some IC models do
- People- Most published designs date back several decades so are in imperial also designs being published now are by people who were bought up on imperial.
ME suppliers tend to stock imperial materials and tooling as thats whats in demand but as imperial materials become harder to obtain I'm sure it will shift over to metric in time.
its-smee17/08/2009 08:38:00
42 forum posts
17 photos
The argument for imperial / metric has been raging for years in M.E.  I personally prefer imperial but use both as and when required. 
Part of the problem is europe. - they can only use metric, so want the world to change to suit them.  We are suffering from "creeping metrication" on a massive scale but no one has recognised this fact.
As a point of interest try dividing a metric measurement by three.   ----    now you see why imperial is best.   
Some talk of millimeters and some of kilogrammes,
and some of decilitres to measure beer and drams,
but I'm a british workman,too old to go to school,
so by pounds i'll eat,and by quarts I'll drink,and
I'll work by my three-foot rule
                                ( Rankine 1874 )
John Stevenson17/08/2009 08:59:02
5068 forum posts
3 photos
Another example of the flat earth society.
John S.
David Clark 117/08/2009 09:34:30
3357 forum posts
112 photos
10 articles
Hi There
I will continue to publish in imperial and metric for the forseeable future.
Many contributors write in imperial because they are well into their sixties and that is what they were bought up with.
Some contributors write in Metric and others supply drawings with both systems on.
I expect you will all be working in imperial long after I am gone.
regards David
its-smee17/08/2009 09:35:49
42 forum posts
17 photos
I assume JS that you are a founder member of the flat earth society.  If you can't make constructive comment - then don't.  Do not drag this forum into a slanging match like so many other forums.  If you wish to make negative comments then I suggest you go elsewhere
Kieran Sparks17/08/2009 09:44:53
5 forum posts
As Younger Model engineer at 23, sorry gentlemen........
I can see how Imperial would be a shock, as most school's teach metric now as a matter of course. Plus the wider world is using said materials and machines.
Althought here are a few points..........
Model engineer magazines before my time and with original LBSC's designs are all Imperial, going back well beyond 1930.
Unless you want to scratch build or chew parts out of solid for a Model, you will have to buy castings. Which will mostly be cast off original wooden patterns scaled to Imperial plans.
All the current designs for locomotives either 3 1/2 or 5 inch gauge run on imperial track gauge. It is unlikely that clubs are going to relay track or that plans for locomotives are going to be revised into Imperial, due to cost and manpower.
by any rate alot of Imperial plans have never been revised and still have errors on them. Popular designs as well, but this would mean owning up to errors and probably legal? The majority of people in clubs will know something about one or two designs. This is where it is invaualable to talk to somebody about the model you are planning.
How I get round Imperial
I work on a Imperial myford, and I am completly metric, so work with what you have.
I tried to make the transition easier by these few methods and it does not cost the earth.
If all else buy a Digital vernier caliper ( machine and a copy of Zeus tables.
I find that breaking Imperial down into a decimal much easier to understand than the fraction eg 1/2 = 0.500  or 1/8 = 0.125 althought the read out will give you a fourth digit after the point, i dont tend to work down to that tolerance. Some drawing you may find are written in Imperial decimal, so dont get caught out thinking it is metric. 1/8 can also be written in this case as .125  (point only in front ) Zeus will give you decimal breakdown of the sizes in a table, but for quick refernce if you use a caculater dived the top number of the fraction into the bottom. ie 3/16 would be 3 divided by 16= 0.1875  The talbes are extremely useful for reference including letter and number drills which are also gauged in standard metric sizes, good for working out to drill undersize for reaming Imperial.
( I have no machine fitted with Dro, and i still prefer to work with an eyeglass when marking out with a manaul read off vernier height gauge. Althought i did invest in a digital micrometer recently, but i find it is not as accurate as normal thimble type moore and wright types.) 
With my Zeus tables, I photocopied it and made it larger to A4 and have two polly pockets one for each page, so i can refer to it easily. I dont go anywhere in the garage without these. On the reverse of each page I also have a print out of information.  One consists of BA (British Association)sizes for tapping and threading and the other is for ME(Model engineer standard and special fine thread) sizes. This information is available in many places ie the back of the blackgates catalogue for free or on the net.
Apart from these pages i work on little else to complete my work. They are my bible, even with constant referal i still probably couldnt tell you all the decimal breakdowns off all the Imperial sizes, Its like a second langauge still. My maths is prity shocking so if i can work in Imperial, im of the opinion that with practice and a little patience it can be done.
 I hope my waffle is a little insightful to the complete begineer and i apolgise to the more learned than I. (ie teaching granny)


Edited By Kieran Sparks on 17/08/2009 09:46:38

Edited By Kieran Sparks on 17/08/2009 09:48:15

Edited By Kieran Sparks on 17/08/2009 09:49:19

Ian Abbott17/08/2009 10:29:02
279 forum posts
21 photos
At school in the fifties, we were taught all measurement systems, Imperial, metric, avoirdupois, paper, rod, pole, perch, nautical, bushels, pounds, shillings and pence, Roman numerals.................
I feel more comfortable with Imperial, but whatever is on the paper is what I work with.  It 'aint difficult.  If you are using a decent CAD program, a click of the mouse changes everything to whichever.  Digital calipers do the same. I have a cheap calculator which does the conversion math for me nowadays on account of the brain atrophy.  I have rulers and verniers in both Imperial and metric, which I can't read without a watchmaker's loupe.
I worked for years in Canada, which is metric ('cos of the minority in Quebec, but don't get me started) but most of the materials and equipment came from the States, we coped.  If I'm shopping, 25mm is about an inch, 13mm, half an inch,  100m, a bit more than 100yd, 1k, 5/8 of a mile........     My bike speedo came from India, it's in kilometers:  50k= 30mph,  80k=50mph.  The bus I ride on when it's raining has a tachograph, marked in kilometers, but the bus driver doesn't care, 'cos the bus won't go fast enough on Devon country roads to be speeding.
In the end, it's all just numbers. 
Circlip17/08/2009 11:33:51
997 forum posts
Sorry its-me, your Moderator name check is missing, perhaps one of the OFFICIAL moderators should have made a comment IF neccesary!
 The good ole imp/met debate will perpetuate while ever people have to go to the toilet. With all the reliance on DRO's, whats the problem?? If the drawing is in Metric, set the numbers and then press the convert button and vicky vercky.
  Had to become bi- sexual with numbers in the early sixties, initially it was freezing, but once in there we soon became accustomed to it.
  Had to become Tri- sexual with currency, but can still work it out WITHOUT an electronic number cruncher and I don't need a Till with pictures of the goods on the keys to be able to add up the cost of three pints, two bacardi and cokes and a packet of Pork Scratchings BEFORE the barmaid has squirted the first pint into a glass, and yes, sixty is a memory.
   Regards  Ian.
chris stephens17/08/2009 11:45:50
1045 forum posts
1 photos
I think you should work in whatever units you like, be it Metres, Feet or Cubits. They are afterall just numbers. Anybody who calls themself an engineer, be it Pro or Am, who can't convert from one to another is quite frankly a Numptie. There are books, calculators, DROs, digi-calipers and computer programs, not to mention mental arithmetic that can be used to switch units.
Personally I use whatever unit is most convenient, anything so I don't use fractions any smaller than eighths, that is until micrometers and lathe dials read in fractions. Purists will say you should not mix Imp with Metric, well I say why not, to repeat, they are just numbers. Proviso  here is of course that all units are clearly marked. Logically it is no more stupid than using Metres and Milli-Metres in the same drawing. If it is confusing to mix IMP and Metric, then Numpties will be confused by divding/multiplying by 1000 too.
The human brain likes to think in whole numbers. It sees 1" and likes it, but show it 25.4mm and it thinks "Oh dear". Show it 25mm and it is happy, but show it 0.984",  "how am I going to turn to that accuracy?" Get the point?
I wish people would stop whinging about one system should be used to the exclusion of all others. It really does not matter a jot, so GROW UP. 
chris stephens
its-smee17/08/2009 11:52:35
42 forum posts
17 photos
   I too can add up the drinks bill before the barmaid with her "visual aids" and like you was taught all measuring systems. I swap and change btween the two on a daily basis, just depends on the task at hand.  I was not trying to be a moderator but the comment by js was not necessary. If you can't make constructive comments , then don't, its as simple as that.
Paul Atkin17/08/2009 14:25:22
7 forum posts
Some interesting points, but I would take exception to the comment;
Posted by its-smee on 17/08/2009 08:38:00:

Part of the problem is europe. - they can only use metric, so want the world to change to suit them.  We are suffering from "creeping metrication" on a massive scale but no one has recognised this fact.
As a point of interest try dividing a metric measurement by three.   ----    now you see why imperial is best.   
 It's nothing to do with Europe - I work in Japan - it's been metric for over 100 years, so to is ALL of Asia, India, Africa the Middle East & South America.
 Why so anti metric?  The sooner the USA and to a lesser extent the UK catches up with the rest of the world and we get one standard easier it would be.  Anyone read about the Gimli Glider?  Even NASA have finally realized this after crashing a couple of spacecraft.
Well, I would like to see how you would split an inch into 3?  Would that be 2 and a bit eighths, or 5 and a bit 16ths or 333.33333333 recurring  thou?
its-smee17/08/2009 14:58:59
42 forum posts
17 photos
much of the far east / australia used to be imperial as a result of the influence of the now defunct british empire. many area's still use the imperial system and the metric system together just like we do in the u.k. 
as for dividing an inch by 3 - it would be 4/12   . The imperial system is far more versatile in its use.  to say it is 2 and a bit eighths  or 5 and a bit sixteenths just proves we still need to continue teaching both systems and let people make a free choice as to what system they use and not be forced to by goverment
John Ladlow17/08/2009 16:28:44
17 forum posts
"as for dividing an inch by 3 - it would be 4/12 "
How about 1/3?
But this just shows the problem. How do you measure 1/3 accurately to .001 (or even 0.0001)?
The answer is that you would use decimals which takes us back to the original argument.
If you are going to use decimals, then the metric system is far more logical with everything in multiples of 10.
I was taught imperial, but switched to metric for my own stuff years ago. I still use imperial  when I use drawings drawn that way and it is a pain.
JasonB17/08/2009 16:44:42
16922 forum posts
1818 photos
1 articles
"As a point of interest try dividing a metric measurement by three.   ----    now you see why imperial is best. " 
you probably would not as 1:3 is not a ISO scale. You would use 1:2, 1:5, 1:10, 1:20, 1:50, etc
And even at 4" scale or 4inch to the foot one inch is not an easy size to get at using fractional inches so you have to compromise with 5/16 or 3/8 if you want to use stock material sizes
John Stevenson17/08/2009 19:27:35
5068 forum posts
3 photos
Posted by its-smee on 17/08/2009 09:35:49:
I assume JS that you are a founder member of the flat earth society.  If you can't make constructive comment - then don't.  Do not drag this forum into a slanging match like so many other forums.  If you wish to make negative comments then I suggest you go elsewhere
 Why would you want to divide a metric or decimal measurement by 3 ?
Base of metric and decimal is 10
None of my machines imperial or metric  has a scale or dial on it that can be divided by 3
And a 1874 quote by Rankine is hardly relevant in this day and age and again as a point of interest I left the flat earth society when I sold the Reliant, it wasn't you that bought it was it ?
Ian Abbott17/08/2009 20:26:14
279 forum posts
21 photos
This isn't intended to comment either way, but more about not being smart.
In the early nineties, the University of Alberta in Canada had a new theatre built.  Being Canadian, it was built to metric standards.  The measurements in some cases were in millimetres, with values such as 18,288mm.  Which only takes a decimal point or two to make sense of, but why?
The real problem here, even before the building was finished, was that the entire theatre and building industries in Canada work in Imperial measurements.  This was before we had embraced CAD completely, so I was "offered" the task of spending a week at the drawing board with the architect's plans, redrawing the entire building plans and sections from 50:1 to 1/4" scale, so that the templates for lighting and set design could be used.
Then, the really stupid thing was that all the metric measurements turned out to be direct conversions from 8' x 4' sheets of plywood and 4" x 2" dimensional timber, so a 40' wide stage using five 8' sheets of ply, became a 12,192mm stage using five 2,438.4mm sheets of ply.
Nothing wrong with metric/Imperial, as long as the people who use them aren't idiots.
Niloch17/08/2009 20:47:43
371 forum posts
Am I not right in saying that British bricks and concrete blocks are of Imperial sizes?
Circlip17/08/2009 20:56:31
997 forum posts
Yes Ian, sheets of Stainless we ordered at one point were 3mm thick and 2440 x 1220.
  When I cultivated concrete in my garden to act as a landing pad for four motorcycles at the time, I got a good deal on some 2ft x 1ft concrete flags. A few years later, the 600 x 300 to repair a couple look a real dogs dinner.
    Regards  another Ian.
Ian Abbott17/08/2009 20:59:13
279 forum posts
21 photos
Ah, yes, but you can no longer buy a 4" brick or a 2' slab.  They only sell 101.6mm bricks and 609.6mm slabs.

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