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Metric vs Imperial - Practical or Traditional?

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Ian Abbott17/08/2009 21:15:33
279 forum posts
21 photos
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.
The Harper17/08/2009 23:11:13
18 forum posts
12 photos
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!
Paul Atkin17/08/2009 23:36:57
7 forum posts
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)
JasonB18/08/2009 07:41:18
22604 forum posts
2643 photos
1 articles
The biggest metric/imperial annomoly in teh building trade is that plasterboard comes in 1200x2400 sheets and ply in 1220x2440 sheets so if you set your joists to suit teh plasterboard you have to trim 20mm off each sheet of ply
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
Ian Abbott18/08/2009 10:47:09
279 forum posts
21 photos
I believe that my 90 year old Randa lathe was built to the old Stephenson "that's about right" standard, as in standard gauge railways.
its-smee18/08/2009 17:22:02
42 forum posts
17 photos
mgj18/08/2009 18:10:38
1017 forum posts
14 photos
Am I not right in saying that the metric pipe thread is actually BSP? Many metric cars actually use 3/8 UNF on brake fittings.
And the dairy and food industries, who sell their products in grammes and kg,while using a few SMS and DIN fittings, mainly use RJT. Which are imperial.
And the US who still use some imperial (but different in some respects from ours) have a military who have metricated. 
When you buy a car, do you want to know how many kw it has, or do we not all think proper horsepower. Thats decent SAE BHP horsepower, not some DIN european fakery type rubbish. 
There is no more logic in metric than imperial surely? Things happen per unit distance by unit time/area etc or whatever.  People argue that with all to the base 10 its easier. That is so on hte face of it, but start converting from kg to newtons, or using gas laws and constants, or aerodynamic functions. In no time at all you are into "illogical" figures, simply because the physical world is like that. Nowadays with computers or calculators, whether you multiply by 9.81 or 32.2 is really of no consequence.
People argue about dropping the decimal point somewhere with metric -well yesssss. but then the lbs to lbs force and back is to me a lot more dodgy.
So doing engineering calculations I prefer to work in metric.
And when munching metal I think in thous and inches. And mostly use metric fasteners for convenience, and metric drills too.
Who cares- at the end of the day its only a figure on a dial, either way.
As for tooling in inch sizes - well there is a lot of stuff that uses them. No one will change a system of tool holders for some CNC machines. Nor will I buy 6mm tool steel, when all my little holders are 1/4". So hopefully good christian units will be around for a long time to come. 
Then we can all use what we want

Edited By meyrick griffith-jones on 18/08/2009 18:11:20

Edited By meyrick griffith-jones on 18/08/2009 18:18:44

Edited By meyrick griffith-jones on 18/08/2009 18:20:09

Circlip18/08/2009 19:08:53
1502 forum posts
Ahh, but it doesn't seem as much to stick 2P on a litre as 10P on a Gallon
mgj18/08/2009 20:17:45
1017 forum posts
14 photos
More like £4.50, and that, even to this bunch of tax hiking, pension grabbing fiends is £4/10/0d which  they ain't earned but don't stop them spending.
Peter Tucker18/08/2009 22:26:00
183 forum posts
Paul Atkin,
I cannot answer your question, and I would say from the posts recived no one else can, however I would think if someone was to build an exact model they would work in the units used on the original.
So far as metric V imperial if you completly reject one system then, in my opinion your missing out on half the game, one example studding in aluminum needs a robust thread Witworth is a better choise than metric.  Another point to remember is the metric system was created in the laboritory by one man (and the lab is where it works best), where as the imperial system was made piecemeal by workers in "the field" there for is a more practical working system.  I am an excarpenter who trained in imperial but worked most years in metric, my imperial rule had 1/10ths", 1/12ths", and 1/16ths" all biger and easier to read than mms but between them (the inch fractions) giving a finer presision of mesurment.
We have a multitude of standards ( all usefull in their own way) why not embrace them all.
Paul Atkin19/08/2009 01:04:57
7 forum posts
Yes as I mentioned in my opening post - most industrial pipe sizes are still in inches.
Maybe its just me and the fact that I live overseas which causes me to be more sensitive to the variations.  I hate the fact that there are so many different standards.  Its simply not efficient or convenient and must cost industry billions of pounds per day on a global scale.
Its not only metric vs imperial, there are deg Celsius vs Fahrenheit (why does the BBC still quote degF??), differing TV systems, NTSC vs PAL, different voltages and frequencies, different connectors for a mutlitude of electrical devices, incompatible computer software, proprietary designs such as memory cards for digital cameras, region coding for DVD's, BluRay vs HDDVD, Shoe sizing, Imperial gallons vs US gallons........ ARRGGHHHH Rant! Rant! Rant!
If I am thinking only about modelling then the fact that I could buy one metric set of drills, taps and dies is surely far more efficient than having to buy 2 of everything (or more if you start considering whitworth, BA etc).  And then there's storage space which is at a premium for any but the luckiest of modelllers.  I have a multi drawer case with all my metric cap heads, nuts, washers, spring washers in from 2mm up to 10mm all arranged in spearate drawers.  I would need to at least double or treble my storage capacity to work with even one or two of the other "standards", and that's only one simple example.
And one more point Peter, however the metric system was developed, it cannot be worse than using 3 grains of barleycorn to set the "standard" inch.
Please excuse me,  I just get so annoyed by the sheer inconvenience of it all..........
Peter Tucker19/08/2009 10:05:09
183 forum posts


I cant disagree with any thing you have said however the alternatives would be worse, i.e. either no standards as screw threads before Witworth, or the entire species excepting only one standard Witworth, only no metric anything.  As for 3 grains of barleycorn to set the "standard" inch, the acuracy to which standard measures are set has advanced with the need and ability of presison, the same has hapened with metric just not from such antiquated beginings.

The thing that I find frustrating is the mediocre tends to dominate for instance windoz on PCs and VHS over Beta with vidios,  but thats another entirly difrent rant..  Sorry!!

Ian S C19/08/2009 15:10:56
7468 forum posts
230 photos
I believe that the official standard measure in the USA is a one Metre sample held by the national standards organization.IAN.S.C.
mgj19/08/2009 18:28:43
1017 forum posts
14 photos
Ah well - once you have that metric changewheel, you got it made!!!!!
BUT - have you seen a metric thread dial indicator - 3 different pinons, and however many lines and a whole darned chart, just for a few mouldy European threads. 
I rather like the 4 line Imperial job. Any line for multiples of the leadscrew, and opposite pairs for even numbers. Not bad for an illogical system.
Ian Abbott19/08/2009 19:31:42
279 forum posts
21 photos
Hey Ian SC,
The States don't use the metre, they have something called the meter, which I believe is similar and used by the US auto industry.
And, I've just seen the best yet, rail standard gauge (gage in the US) is now 1,440mm. 
russell05/09/2009 08:31:48
142 forum posts
i was surprised the other night when leafing through an old ME (1904, well past its centenary!) to see the first constructional item was imperial (fractions), the next was in millimeters.  
Seems this battle has now overtaken the 100year war....
Ian S C05/09/2009 13:57:09
7468 forum posts
230 photos
Our rail gauge here is still 3'6"and I think itwill stay that way,even if imperial completely disappears from NZ.IAN S.C
Mike05/09/2009 15:51:29
713 forum posts
6 photos
I spent all my working life in the publishing industry, and used to design newspaper pages using another Imperial measurement - ems and points (72 points to an inch, I recall). When the industry changed to the metric standard, I remember going to our suppliers and asking for "a metric ruler about two feet long, please." Points, of course, still survive in the height of computer typefaces. Surprising the "metricate everything" mob haven't got their sticky fingers on that.
Even after more than 30 years working to metric standards, I still think in Imperial. Just an old fogey, maybe!
Terryd05/09/2009 17:12:52
1936 forum posts
179 photos
Bricks Are metric.  215 x 65 x 102.5  (see BS 3921).  That gives a coordinating size in a wall of 225 x 75.  The latter dimension of 102.5 is not a conversion from imperial, but because the width of a brick has to coordinate with the length in certain bonds.  So two widths plus two mortar joints of 10 mm is equal to one full brick with one joint of 10 mm, i.e. 225mm.  Thus the bricks can coordinate.  If you doubt the difference between Metric and imperial bricks I suggest you try matching the two in a sectionof brickwork.  Also slabs ARE 300 x 600. 
As a mid 60 year old I am extremely happy with the metric system and prefer it.  \we can all find fault with all systems such as 'try dividing by three' just try multiplying fractional sizes without converting or dividing decimal imperial by three - no significant difference.  A serious problem with imperial measures is that they were not constant across the world, there were no agreed standards.  Try getting an English quart into an American quart pot. There are also many definitions of a mile, there is no standard.
Frank Hornby used imperial in the late 19th century when inventing Meccano, as one would expect but was specifying grammes (sic) for his weighing experiments.
Please could we also bury this insistence on blaming this vague concept of 'Europe' for metrication it was the British government who decided to adopt the more logical metric system well before 'Europe' was involved with such decisions.  It was made on the recommendation of British scientists, engineers and other interested parties who wanted to be rid of the haphazard, complex and illogical system that is the imperial one and use a simple straightforward system with one length measurement and one volumetric and weight measure.  ( the decimetre, hectolitre etc are made up measures and are not part of the ISO system).
By the way, we use the L as the basis of the pound sterling (£ because it is derived from a French denomination, the Livre, Our system of weights are based on a medieval French system Hence 'lbs' for pound and the avoirdupois ounce etc.  in fact it was the influence of European countries who gave us the Imperial system and they dumped it when a better system came along.  Another by the way, those who think that the inch was the width of Henry the Eighths thumb, just remember he was a Tudor - Welsh / Normans.
Paul Hanson11/11/2009 09:05:46
3 forum posts
This a fascinating debate.  I want to make an observation as someone fairly new to the hobby.
All of the comments are talking about the present (and the past!) - no one has mentioned the future.
How do we attract more people into the hobby? People like myself who are of a generation only schooled on Metric. People like myself with no previous engineering background. I fully appreciate those with a traditional frame of mind - their wisdom and practical experience has been invaluable to a newbie like me. But I have to say when I got into this area I was mortified at how much imperial was still around. I am not commenting on which system is best but where the future is.
I am not saying that Model Eng should try to become hip and nintendo friendly (turbo cad for the DS anyone?) but if we carry on like this it's a dying art.

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