Why is the world of model engineering still imperial?

[Martin KyteParticipant @martinkyte99762]

There are bits that have moved to metric long ago. Low hanging fruit and all that. It’s fairly standard to use drills in the 1mm to 10mm range in 0.1 increments for nearly all drilling operations. Said drill being cheaper and more available.

regards Martin

Oh and clockmaking wheel cutters are Mod now rather than DP

Edited By Martin Kyte on 08/03/2023 13:50:55

[JAParticipant @ja]

Posted by derek hall 1 on 08/03/2023 13:43:36:

A branch off this thread would be "the future of model engineering?"

Both my sons in law (in their early30's) have no idea about "practical" stuff let alone have engineering skills or the pro's and cons of metric or imperial measurement.

Houses are getting more expensive for the younger generation and those that have a garage or even a garden big enough to put a shed in suitable for a workshop are at a premium. If you live in rented accommodation then its even harder to create a workshop. Not even factoring in the cost of machine and hand tools against the cost of living and bringing up a young family for example.

I do not want to change the direction of this thread but I think there maybe a part of imperial measurements that may turn off budding model engineers (young and old).

The days of coming home from work having your tea and going out to the "shed" to bash some metal have changed dramatically.

But the world of Model Engineering is slowly, albeit very slowly turning metric thanks to new published designs (thanks to Jason and others!) – I think this makes the design more accessible and understandable to the metric only generation……and they are the future model engineers

No. That is a new topic and I have been resisting starting it for a few days. At present I have got my hands full with the minor disasters of life (not weather or health related).

JA

[Harry WilkesParticipant @harrywilkes58467]

Posted by Jelly on 08/03/2023 12:33:24:

Posted by JA on 08/03/2023 11:49:20:

The younger generation have, in general, little knowledge of Imperial units and don't want to know.

I'm not sure this is true, at least in Britain it's still pretty common for young people (who do anything remotely practical at all) to have good familiarity with both imperial and metric systems, and to be able to convert between the two freely.

Most of us* prefer metric, but as long as America exists we have to be conversant in both and the US influence on young people has if anything grown as a result of the internet making "the pond" a lot smaller in people's digital lives.

​

When you get to young people who are being trained in engineering occupations, unit conversions are still considered a fundamental skill they love to drop into the curriculum to catch people out at every level right up to people doing MSc/MEng… At least for people in the process industries.

Because in real life you have to work with systems that were designed anywhere from 1840 to the present day, and built all over the world.

So you may well find yourself having to modify or integrate with an assembly originally built when your grandfather was your age, which now has different components specified by long since defunct OEM's in SI, CGS, US Customary, Imperial, and drawn to three or four different standards.

​

That latter point is why I don't get why metrication of the hobby really matters… In real life the existence (and continued promulgation by Americans) of the imperial system is just something you deal with.

*Yes, I'm claiming to be a young person, but being early 30's that statement is somewhat relative.

Edited By Jelly on 08/03/2023 12:36:01

The younger generation have, in general, little knowledge of Imperial units and don't want to know.

I'm not sure this is true, at least in Britain it's still pretty common for young people (who do anything remotely practical at all) to have good familiarity with both imperial and metric systems, and to be able to convert between the two freely.

Agreed that's what I suggest earlier but they were described as being 'very bright'

H

[File HandleParticipant @filehandle]

When I was teaching computing I noticed that students had a hard time adopting different number bases: Binary, Hex etc. Eventually I put this down to only having had a denary educate and not having had the experience of the different fractions used in Imperial system. There can be advantages in being exposed to more than one system.

[Speedy Builder5Participant @speedybuilder5]

Martin – Tracy tools (others available) Imperial drills same price as metric ie HSS 1/16" – 1/2 inch by 64ths £30 (29 in a set) and Metric 1mm – 13mm x 0.5 increments £25 (24 in a set). So ignoring any slight differences, metric same price as imperial – £1 per drill on average.

Bob

[SillyOldDufferModerator @sillyoldduffer]

Posted by Jelly on 08/03/2023 12:33:24:

Posted by JA on 08/03/2023 11:49:20:

The younger generation have, in general, little knowledge of Imperial units and don't want to know.

I'm not sure this is true, at least in Britain it's still pretty common for young people (who do anything remotely practical at all) to have good familiarity with both imperial and metric systems, and to be able to convert between the two freely.

…

I'm getting the impression that some think the slim list of straightforward units encountered in ordinary life are the Imperial system, and may not be aware Imperial is far more extensive than that. Inches, pounds and pints are just the tip of an iceberg. It's what's below the waterline that's the problem.

I have a high opinion of young Jelly, and wonder if he would mind listing the units he thinks comprise the Imperial system. For the avoidance of doubt, it would reveal if we're talking about the same thing! I'm against Imperial as used in professional engineering, not inches measured in home workshops by chaps who only do basic engineering mathematics!

If any Imperial supporters are interested in plumbing the depths, I'll post a few exam questions from my collection of 1930's textbooks. I've done this before, and they're usually ignored – too difficult! However, important to realise that recommending Imperial to youngsters, means the whole system is being pushed, not just the icing on top!

Anyway Jelly, what do you think the Imperial system is? Without looking anything up, please list the units you know how to use.

Ta,

Dave

[larry phelan 1Participant @larryphelan1]

Whatever about model engineering, fullsize practice seems to have almost totally Metric.

Around here, to look for Whitworth fixings would be like looking for Unicorn droppings, most supplier seem never to have heard of them, [the Whitworth stuff, not the droppings ]

I need a simple 3/8" whitworth screw/bolt a few days ago and went to my good old box full of screws, bolts, nuts ect, the type of things which "will come in handy some time " There must be two hundred or more items in there, but was there even one 3/8" whitworth ? You must be joking ! everything else, Bsf, Unf, Metric fine, others that I dont know what the hell they are.

However, the Gods took pity on me when I found one still cling to an old frame in my scrap box.

So, good as the system was, it appears to have had its day.

I rest my case, and put on my tin hat !!!

[JellyParticipant @jelly]

Posted by SillyOldDuffer on 08/03/2023 15:33:45:

Posted by Jelly on 08/03/2023 12:33:24:

Posted by JA on 08/03/2023 11:49:20:

The younger generation have, in general, little knowledge of Imperial units and don't want to know.

I'm not sure this is true, at least in Britain it's still pretty common for young people (who do anything remotely practical at all) to have good familiarity with both imperial and metric systems, and to be able to convert between the two freely.

…

I'm getting the impression that some think the slim list of straightforward units encountered in ordinary life are the Imperial system, and may not be aware Imperial is far more extensive than that. Inches, pounds and pints are just the tip of an iceberg. It's what's below the waterline that's the problem.

I have a high opinion of young Jelly, and wonder if he would mind listing the units he thinks comprise the Imperial system. For the avoidance of doubt, it would reveal if we're talking about the same thing! I'm against Imperial as used in professional engineering, not inches measured in home workshops by chaps who only do basic engineering mathematics!

If any Imperial supporters are interested in plumbing the depths, I'll post a few exam questions from my collection of 1930's textbooks. I've done this before, and they're usually ignored – too difficult! However, important to realise that recommending Imperial to youngsters, means the whole system is being pushed, not just the icing on top!

Anyway Jelly, what do you think the Imperial system is? Without looking anything up, please list the units you know how to use.

Ta,

Dave

Honestly, I couldn't truly differentiate between "Imperial Imperial" and US customary at this point, other than knowing through bitter experience to ask "Which Gallons" or "Which Tons" when someone tries to use those units.

I know this won't be truly complete, but should be a fairly good cross-section, so let's have a crack…

Mass:

• Grain, [interstitial base 16 unit I can't remember the name of] Oz, Lb, Stone (people only), Cwt (I actually find hundredweights oddly intuitive to estimate the weight of big things), Tons, [avardopoidis sp? versions of the same].

Volume:

• [weird appothacaries units], flOz, Pint, Quart, Gallon, [comical brewing barrel sizes], bbl (strictly it's an oilfield unit, but it's defined in US Gal), cuYd, cuft

Pressure/Force:

• Psi, KSI,

Length:

• "mil", "tenth", "thou", Inch, Foot, Yard, Mile, Nautical Mile (still in use in metric too because it's defined conviently via something to do with arc-seconds of longtiude).

Area:

• Acre, sqft, sqin, square mile

Power:

• hp, lb*ft/s, BTU/hr

Energy/work

• lb*ft, BTU,

Force:

• lbf, poundal (might be the same as lbf, Slug (not the same exactly but the unit of mass which gives the imperial system it's equivalent of 1kg = 9.81N equivalence for gravity), kip (us customary unit used for statics calcs in steelwork)

Torque:

• lb-ft, lb-in, oz-in (not the same as lb*ft, thanks whoever decided on that convention!),

Radioactivity units:

• Curie, Rad & Rem (just URGH, because radiation protection was just soooooo simple before that I needed the unit conversions to spice it up right?).

From there you get into the compound units in imperial, many of which would be derived units with their own name in SI and CGS (in this regard imperial can be better when you're trying to ensure an analytic solution or non-dimentionalisation makes sense), like lb*s/ft² (or lbf*s/ft² because people couldn't agree) for viscosity (the reyn might be a dynamic viscosity unit in imperial actually, it's that or stokes but I'm pretty sure the stokes is CGS), which are actually what I encounter most in an engineering context.

Most of the plants I've worked on over the years have had at least some parts which were developed pre-metrication (in which case it's a CGS vs. Imperial toss-up) or during metrication (urgh, CGS), it's also really common to see upgrades to UK and European plants which have integrated equipment from American and Canadian vendors, which is designed and specified in US customary units (which isn't Imperial, but is close enough to trap you).​

 

I would wholeheartedly agree with your statement:

Posted by SillyOldDuffer on 08/03/2023 15:33:45:

I'm against Imperial as used in professional engineering,

…

as long as we can chuck US customary units in with Imperial.

I don't mind either in a historic context, as it's a trade off for some quite cool opportunities to get up close with artefacts and living history which allows me to see the evolution of different industries (and how long some equipment lasts) first hand…

But for the love of god stop deliberately using them in new designs for sale to the international market!

[JellyParticipant @jelly]

Oh, forgot the "inches of [insert substance here]" pressure measurements, in-hg and in-h2o being common in different fields.

[Clive SteerParticipant @clivesteer55943]

I've got some scruples if anyone still uses this unit of mass.

CS

[Clive SteerParticipant @clivesteer55943]

The American gallon is smaller than the Imperial so does that mean their pints are as well.

[norm nortonParticipant @normnorton75434]

Goodness me, eight pages of postings. Well, proved myself to be as guilty as the rest of you thinking this is interesting.

But I am intrigued by the thought that a youngster raised in metric will find the use of imperial to be a barrier. Do we really think that? Mmm, I don't know.

I, like most all of you, switch between imperial and metric and enjoy the flexibility it brings. My eldest and youngest sons, who are 39 and 33 years old respectively, happily talk to me in both measurements; one is a builder the other a design engineer. They did not use imperial at school. So does youngster mean under 25 years old?

If you are going to build a model locomotive there are massive learnings to do with machining, materials, soldering, painting. etc. Is the measurement system going to stop you? Well, yes if you just don't want to go there.

Many of us think that scratch building a 5" steam loco is an interest that is dwindling anyway, never mind the measurement units.

Norm

[Roderick JenkinsParticipant @roderickjenkins93242]

The US pint contains 16 fluid ounces I.e. 1 lb of water, which does at least seem more consistent than the Imperial version.

Rod

[Martin KyteParticipant @martinkyte99762]

Posted by Clive Steer on 08/03/2023 17:57:51:

I've got some scruples if anyone still uses this unit of mass.

CS

Isn’t that a volume measure?

[Clive SteerParticipant @clivesteer55943]

No. A scruple is equal to 20 grains a measurement of weight/mass used by Apothecaries.

CS

[Martin KyteParticipant @martinkyte99762]

Definition now I’ve looked it up is it can be fluid volume or weight. Another nail in the coffin.

There is an apothecary measure defined by the amount of dry substance such as chopped herb you can pick up between thumb and forefinger but I’m blowed if I can remember the name. It was remarked on by Steven Maturin in one of the Aubrey/Maturin novels by Patrick O’Brien.

regards Martin

[david bennett 8Participant @davidbennett8]

Posted by Martin Kyte on 08/03/2023 19:46:02:

Definition now I’ve looked it up is it can be fluid volume or weight. Another nail in the coffin.

There is an apothecary measure defined by the amount of dry substance such as chopped herb you can pick up between thumb and forefinger but I’m blowed if I can remember the name. It was remarked on by Steven Maturin in one of the Aubrey/Maturin novels by Patrick O’Brien.

regards Martin

Pinch? (= 2 smidgens)

dave.

[Martin KyteParticipant @martinkyte99762]

Posted by david bennett 8 on 08/03/2023 20:29:16:

Posted by Martin Kyte on 08/03/2023 19:46:02:

Definition now I’ve looked it up is it can be fluid volume or weight. Another nail in the coffin.

There is an apothecary measure defined by the amount of dry substance such as chopped herb you can pick up between thumb and forefinger but I’m blowed if I can remember the name. It was remarked on by Steven Maturin in one of the Aubrey/Maturin novels by Patrick O’Brien.

regards Martin

Pinch? (= 2 smidgens)

dave.

No I’m sure it was less obvious than that, Steven had finally got one over on Jack Aubrey for all his naval terminology so it was definitely something obscure.

regards Martin

[Michael GilliganParticipant @michaelgilligan61133]

You may find it here, Martin **LINK**

https://en.wikipedia.org/wiki/Approximate_measures

… or it might be really obscure !!

MichaelG.

[Martin KyteParticipant @martinkyte99762]

Oh it’s definitely really obscure. I remember at the time I must learn that word but have since forgotten as you do with anything you don’t use.

I will find it eventually as I read all 20 books every 2 or 3 years.

regards Martin

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by Martin Kyte on 08/03/2023 20:53:51:

I will find it eventually as I read all 20 books every 2 or 3 years.

Me too!

Rod

[CirclipParticipant @circlip]

Yes Norm, eight pages and would be a darned sight less if we could refer to a post # rather than cut and paste vast lines of text.

Sorry Jason, my ref to 1/8"- 0.312 Should have been 1/8" OR 0.312 (0.3125 if working for NASA which many think they are).

Unfortunately the designs that the O/P seems to favour are 'Old school'. Yes, there are metric designed models but are precisely that and not 'Conversions'. Years ago, I had a hard time trying to convince an American colleague that an unimportant dimension of 25mm didn't mean he had to cleave 0.4mm OR 16 thou from a 1" bar of metal.

Regards Ian.

[JasonBModerator @jasonb]

Posted by Circlip on 09/03/2023 11:34:08:

Sorry Jason, my ref to 1/8"- 0.312 Should have been 1/8" OR 0.312 (0.3125 if working for NASA which many think they are).

But an 1/8" is not 0.312, should it have read 5/16" or 0.312" = 7.9375mm.

 

Edited By JasonB on 09/03/2023 11:49:07

[SillyOldDufferModerator @sillyoldduffer]

Posted by Jelly on 08/03/2023 16:37:45:

Posted by SillyOldDuffer on 08/03/2023 15:33:45:

Posted by Jelly on 08/03/2023 12:33:24:

Posted by JA on 08/03/2023 11:49:20:

The younger generation have, in general, little knowledge of Imperial units and don't want to know.

I'm not sure this is true, at least in Britain it's still pretty common for young people (who do anything remotely practical at all) to have good familiarity with both imperial and metric systems, and to be able to convert between the two freely.

…

I'm getting the impression that some think the slim list of straightforward units encountered in ordinary life are the Imperial system, and may not be aware Imperial is far more extensive than that. Inches, pounds and pints are just the tip of an iceberg. It's what's below the waterline that's the problem.

…

Anyway Jelly, what do you think the Imperial system is? Without looking anything up, please list the units you know how to use.

Ta,

Dave

…

A good answer from Jelly, who's understanding of Imperial goes some way under the waterline! I suspect his list is more comprehensive that most. Slugs are in there, so perhaps I was wrong to assume Harry Wilkes youngsters must be extra smart to know about them! Personally I find slugs, blobs, pounds (two meanings!), poundals and pounds-force confusing, as was the painful way the metric system got to it's present relative clarity!

But there's much more to Imperial than Jelly's overview. Drilling into Energy, Work and Power, in addition to lb*ft and BTU, there's the Therm and calorific value in BTU per cubic foot. Temperature is measured in Fahrenheit. The Mechanical Equivalent of heat is 772 foot-lbs, and one Horse Power is 33000 foot-pounds per minute (550 ft-lbs per second). So if 1lb of coal of heat value 15,000 BTU delivers about 12,000,000 ft-lbs per hour, which is 200,000 ft-lbs per minute, or 6.06HP. 6.06HP doesn't mean much to an electrician, but all we have to do is multiply by 745.7 to get the answer in watts (4518.942) This system caused trouble from the outset, because the scientists who determine fundamentals like calorific values, specific heats, and other basics always work in metric, making it necessary to answer questions like:

How many calories are equivalent a therm? (1lb = 453.6g. 1 cubic foot = 28,317cc)

and

How much energy, in foot tons, is given out when 1lb of steam condenses? (1lb liberates 965BTU).

Even more awkward arithmetic needed if the answer is needed in inch ounces, another valid imperial unit:

The problem is the number of conversions generated by illogical relationships within Imperial measure. 'Magic numbers' are constantly required: 33000, 772, 550, 745.7 mentioned above, and many others. There are 231 cubic inches in a gallon, but is that a US or a UK gallon? 1728 cubic inches in a cubic foot. 46656 cubic inches in a cubic yard. How many feet per second is 1 mph?

Hard to understand why anyone defends this system, look at the detail and it's a mess!

Dave

[duncan webster 1Participant @duncanwebster1]

Dave,

Just accept it, belief in the Imperial system is like a religion, not open to rational argument. In your moderational capacity you'd better close this down before the howls of protest.

Edited By duncan webster on 09/03/2023 14:00:54

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