Why is the world of model engineering still imperial?

I use both systems, whichever is best for what I am doing. Sometimes both on the same job.
As an ex teacher and examiner, I was amased how poor a typical GCSE student was at manipulating metric units. It may be easier, but beyond the average student.

It is slowly becoming less available, sheet is now almost completely metric in thickness, many of the old copper tube sizes used for boilers are no longer made so you have to roll your own from nearest metric thickness above the swg of the old tubes . As for those beloved BA fixings quite a few now are coming with metric hex heads which although often close are not the same.

You will also find that metric material is cheaper than a similar imperial size eg 25mm 230M07 is cheaper than 1" EN1A. Same with tools - how many imperial tools seem to be sold by the cheap far eastern suppliers and industrial suppliers over here don't keep much imperial these days

Do you really think that metric engineers/machinists/fabricators/etc can't do that, or judge by eye to similar precision?

Why do you say that the model engineering world is still imperial? It all depends on the individual's preference, How many model engineers do you know who prefer to use imperial measure and how many use metric?

Sure, the history of model engineering is imperial for obvious reasons. You should not take this as a justification for your sweeping statement.

Andrew.

Is that why so many of those old imperial drawings don't mention fits and tolerances

I'm 57 and have been model engineering since I was in my teens. Never really used the imperial system unless I really had no choice, like building a Stuart Turner model! Maybe a career in molecular biology and medicine is part of the reason, as imperial measurements were abandoned a long, long time ago in these disciplines.

I learned so long ago to work interchangeably in both sets of units that it matters little to me any more - there are not many opportunities for confusion unless you really don't know the scale of the drawing you're working to.

But I do enjoy the expression of baffled annoyance that comes over younger faces when I talk about a dimension in thous - or worse, 64 ths.

...and the way it clears when I give 'em a metric equivalent.

Yes actually. Don't care what language you speak, the 0-5 thou difference either way is infinitely easier to account for without looking anything up. Remember the focus of this forum is the hobby engineer, not the daily jobber.

I know that up to a couple thou interference, I'm probably ok with the mallet, any more than that and I'm going to the press, no charts required. You can only do that in metric if you already know the values, which are a lot less simple than 1 or 2...

J

A short amble down the road from my house, there is a railway bridge over the road, on the Brighton to Lewis line . On the side of the bridge is a plaque giving the distance in chains from the Terminus. Network Rail obviously still working in the Stephenson age.

The latest MEW features a lathe clutch article regurgitated from ME of decades ago. Nothing wrong with that, it's a good idea. I nearly made it when the original article appeared but now I've got roundtoit! It's now half finished as my latest project. The relevance of this is the dimensions used in the article. To work out how long a piece of stock to cut off for one part, its necessary to add 3 fractions all with differing denominators. I find that the most extremely annoying part of the Imperial system.

John

I spent my working life as a toolmaker. Probably half in imperial and half in metric based units as things changed over. I have no prefference until it comes to reading a depth micrometer. Instant with an imperial instrument but stop and look twice with a metric instrument. Nothing wrong with the measuring tool just my comfort zone.

Edited By Chris Evans 6 on 03/03/2023 20:03:08

You can feel a thou with your finger.
You can still feel a thou when it’s 25.4 microns.

Beats me what all the fuss is about, it’s all just numbers.

No, it's because model engineering is not about mass producing interchangeable parts but making one off models where each part is made to fit its mate. Pre-metric modellers had enough common sense and ability to work out what they needed to know and just got on with it.

BTW in case people are not into music many great composers of previous centuries did not always write down every note of a now great orchestral work. They jotted down the main melody and key parts and the experienced orchestra were able to figure out the details.

Edited By Bazyle on 03/03/2023 20:45:00

Jason! Oh to be living in such an enlightened country!

Over here (Canada) our main stocks of material come from the USA, so getting 25mm 230m07 or an equivalent steel, would have to shipped from Europe. Almost all materials are inch based. USA is 10x the population, and probably 50x the productivity, so...

From a practical and cost savings and resuable part sizes perspective what is your opinion on imperial versus metric engineering uses. Does metric lead to parts looks similar but just not the same in measurements in comparaison to imperial. I always wondered about this.

Transatlantic arrogance creeping in? Population of USA 332 million, population of EU 447 million, UK 60 odd million, plus all the other countries in the world who use SI. As I've said before, this thread has become pointless, no country in the world is going to revert to imperial, it will die outside the USA when the last old crusty shuffles off this mortal coil, and good riddance (to imperial, not the crusty)

I've no recollection of what we measured things in @ school, should have been metric i guess, but i've always done a rough in head conversion depending on what i was measuring. (now a more exact conversion with attempting to be a hobby machinist)

Flit from one to the other.

Big things~ feet.

Under one foot, i find cm convienient.

Little things~ well a thou or ten seems a lot more convienient than .0..whatever mm.

The Imperial system was,at least in part developed from the natural order of things?an inch~ width of your thumb, a foot~ well self explainatory as long as you have large feet , etc etc.

The Metre as i understand it, is the length it is because someone just decided it was so & bears no real relevance to anything real world. They just said a metre is 'this much' & we'll use that.

Metric system short changes you 4" x2" x 8ft Timber? you'll be lacking on all dimensions with metric.

Ever run the mile? Nowadays it's usually the 1500m.

All that said Duncan's probably right, the Imperial system will likely peter out eventually, when all the old & wise have departed this life.

Sometimes the' best' isn't the popular choice. Anyone remember VHS & Betamax?

Betamax was actually technically a better system, whilst being smaller, but Jo public went with VHS.

Hi, not exactly, Betamax was the better system, but VHS won the battle because for whatever reason, more films were made commercially that the public could buy or hire, only a small fraction were for use on Betamax machines.

Regards Nick.

P.S. Betamax machines were more expensive at the time though.

Edited By Nicholas Farr on 04/03/2023 07:01:24

Agree with the way it's done in most home workshops, read any of my build threads and you will see me using one part to gauge the fit of another.

Many a pre metric modeller would seem to have an engineering background based what many members post here so would have been taught about fits etc. Now most coming into the hobby won't have gone through the apprentice system and may not even have done basic metalwork at school, they may have as much common sense but need to know how to apply it.

Funny enough I find the German and to a lesser extent the American drawings tend to give tolerances a lot more than UK ones which have very little and you may need an accompanying text to see if a part should be bare of full but I've yet to find a mic that reads in those amounts be it a metric full or an imperial full but the old boys would have known by the feel of their firm leg callipers as an even older boy would have taught them..

Surely the claim that understanding the values 0 to 5 thou is better than the metric equivalent is simply personal preference. As someone who had to work in both units for most of my working life I know that 1mm is about 40 thou (39.37, close enough for estimating which is what people are suggesting here) so 4 thou is about 0.1mm 1 thou is about 0.025mm. I can add 0.1 and 0.025 and combinations of these to get 1, 2, 3, 4, 5 thou, and vice versa, without having to resort to paper and pencil or calculator.

Martin C

I strongly believe fits and tolerences have a place in model engineering but I am at a loss to understand their relevance to the Imperial -v- Metric arguement.

Perhaps they are being used just to spice up this ancient, pre-deluvian, arguement.

JA