Metric vs Imperial – Practical or Traditional?

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Metric vs Imperial – Practical or Traditional?

This topic has 297 replies, 69 voices, and was last updated 28 August 2017 at 18:05 by Philip D.

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17 August 2009 at 03:18 #42910
Paul Atkin
Participant
@paulatkin73780
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?
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17 August 2009 at 03:18 #4737
Paul Atkin
Participant
@paulatkin73780
17 August 2009 at 07:33 #42912
JasonB
Moderator
@jasonb
-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.

Jason
17 August 2009 at 08:38 #42913
its-smee
Participant
@its-smee
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 )
17 August 2009 at 08:59 #42914
John Stevenson 1
Participant
@johnstevenson1
Another example of the flat earth society.

John S.
17 August 2009 at 09:34 #42916
David Clark 13
Participant
@davidclark13
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
17 August 2009 at 09:35 #42917
its-smee
Participant
@its-smee
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
17 August 2009 at 09:44 #42918
Kieran Sparks
Participant
@kieransparks65317
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 dro-co.uk) 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
17 August 2009 at 10:29 #42919
Ian Abbott
Participant
@ianabbott31222
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.

Ian
17 August 2009 at 11:33 #42921
Circlip
Participant
@circlip
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.
17 August 2009 at 11:45 #42922
chris stephens
Participant
@chrisstephens63393
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.

Discuss!

chris stephens
17 August 2009 at 11:52 #42923
its-smee
Participant
@its-smee
Circlip

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.
17 August 2009 at 14:25 #42927
Paul Atkin
Participant
@paulatkin73780
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?
17 August 2009 at 14:58 #42929
its-smee
Participant
@its-smee
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
17 August 2009 at 16:28 #42931
John Ladlow
Participant
@johnladlow78959
“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.

John
17 August 2009 at 16:44 #42932
JasonB
Moderator
@jasonb
“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

Jason
17 August 2009 at 19:27 #42935
John Stevenson 1
Participant
@johnstevenson1
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 ?
17 August 2009 at 20:26 #42936
Ian Abbott
Participant
@ianabbott31222
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.

Ian
17 August 2009 at 20:47 #42937
Niloch
Participant
@niloch
Am I not right in saying that British bricks and concrete blocks are of Imperial sizes?
17 August 2009 at 20:56 #42938
Circlip
Participant
@circlip
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.
17 August 2009 at 20:59 #42939
Ian Abbott
Participant
@ianabbott31222
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.

Ian
17 August 2009 at 21:15 #42940
Ian Abbott
Participant
@ianabbott31222
Sorry, the other Ian got in while this Ian was composing the last post…..

Our steel supplier over at Paignton says that it’s a toss up when an order of material comes in whether they are getting imperial dimensions or metric, could be 1/8″ steel or 3mm steel.

And, what’s the betting that the concrete slab people have someone ’round the back with a grinder, taking 9.6mm of concrete off the 2′ slabs. Some EU regulation no doubt.

This subject could go on forever, I think I’ll restrain myself from posting any more, no matter how much my fingers twitch.

Ian
17 August 2009 at 23:11 #42944
The Harper
Participant
@theharper
Does it really matter? Metric or imperial measurements can be very easily converted to suit your preferred way of working. After all we are all meant to be keen engineering enthusiasts, so a little simple mathematics shouldn’t strain the grey matter too much. It could be worse, you could have no DRO’s with met / imp conversion buttons, only imperial dials when you are working to metric drawings, or even worse no calculators only slide rules!
17 August 2009 at 23:36 #42945
Paul Atkin
Participant
@paulatkin73780
Many of the comments above simply point out the difficulties when using two systems – which was the point I was trying to make.

As for the comments on use of meters and millimeters on the same drawing, that is simply bad design practice and is no different than using two different units on an imperial drawing. It has no relevance to the question of metric vs imperial.

But talk of construction and pipework where you are dealing with an existing infrastructure is entirely different and understandably difficult to transition. But it can be done, where I live, ALL DIY projects such as house construction, garden components and pipework are entirely metric.

When a one off component is manufactured on a lathe or mill as is done in modelling, then there is really no logical reason I can see to use inches. The only non-standard part I can see would be for the use of some modified BA nuts which I believe have a more scale like appearance – but then would it not be possible for a model supplier to manufacture scale nuts based on metric threads?

Which brings me around to my opening question – is it a matter of practicality or traditionalism? (or as I would prefer to call it – sheer bloody mindedness)
18 August 2009 at 07:41 #42946
JasonB
Moderator
@jasonb
The biggest metric/imperial annomoly in teh building trade is that plasterboard comes in 1200×2400 sheets and ply in 1220×2440 sheets so if you set your joists to suit teh plasterboard you have to trim 20mm off each sheet of ply

Jason

PS Paul, the BA series of threads is actually metric. And a very logivcal reason to use inches on a lathe is that 75% plus of lathes are graduated in imperial
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