Why is the world of model engineering still imperial?

[Another JohnSParticipant @anotherjohns]

Posted by duncan webster on 03/03/2023 22:56:17:

……. USA is 10x the population, and probably 50x the productivity, so…

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.

Duncan – apologies, I was comparing Canada's population to the USA; cripes; the state of California has more people than in Canada (last time I checked anyway) – when I moved back from other countries to Canada, bringing my metric tools back with me, it was a bit of a shock when trying to purchase materials. To go down to the local stockist like Jason and get metric bar stock would be a dream come true!

John.

Edited By Another JohnS on 04/03/2023 12:47:34

[Nick WheelerParticipant @nickwheeler]

Posted by Michael Gilligan on 04/03/2023 10:50:57:

Posted by John Abson on 04/03/2023 10:23:35:

[…]

After about half a day, […]

.

0.5 day in Metric Decimal

Fixed that for you. They are NOT the same thing!

[Bantam BillParticipant @bantambill]

How come all my metric sockets are either 1/4”, 1/2” or 3/4” drive.

[Nick WheelerParticipant @nickwheeler]

Posted by Bantam Bill on 04/03/2023 13:42:50:

How come all my metric sockets are either 1/4”, 1/2” or 3/4” drive.

Those drive tools are a Snap-on invention, and were originally available with American sockets. Would you really want to buy new ratchets, extensions and all the other bits that could only be used on metric sockets?

[martin haysomParticipant @martinhaysom48469]

this debate will run for ever. i can use both. i will use what ever measurement are on the drawing my own often have a mix of both it don't matter they are just numbers. metric is not easer than imperial or vice versa. the only time when one is easer is when you don't understand the other.

[Jeff DaymanParticipant @jeffdayman43397]

Oh, they aren't Imperial Bantam Bill! They're 6.35 , 12.7, and 19.05 mm drives. 8^)

Martin Haysom has it right – we just need to be able to work with either system and know some conversion factors. Once learned, this takes very little time to do. Nowadays you can find almost instant conversion from any unit to any unit free in Google, it takes only seconds.

I don't think it will ever be possible to see grass roots America using metric in everyday operations, unless it costs them money directly to remain inch/gallon/pound users. The US car companies have designed cars in metric on a 100 mm grid since the 1980's and use a lot of metric fasteners, but specs for them are published in the USA only in pounds, US gallons, miles per US gallon, feet and inches. If paint makers ever started selling 3.78 litre cans of paint at Ace Hardware rather than gallons, or a 454 gram bag of nails rather than a pound, there would likely be fistfights.

[Harry WilkesParticipant @harrywilkes58467]

Posted by SillyOldDuffer on 04/03/2023 10:40:16:

Posted by UncouthJ on 03/03/2023 19:40:55:

Posted by Nicholas Wheeler 1 on 03/03/2023 18:32:39:

Posted by UncouthJ on 03/03/2023 15:49:00:

Here's the debate ender… Fits n tolerances!

You can pretty perfectly gauge an amount of slop in a slip, or an amount of welly on an interference in a handful of thou. Tell me you can do that so simply in metric so I can call you a liar 😉

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

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

J reveals a misunderstanding of fits and tolerances I fear!

'You can pretty perfectly gauge an amount of slop in a slip, or an amount of welly on an interference in a handful of thou.' isn't working to a tolerance, it's "Fitting" in the old fashioned sense. This is not working to a tolerance, because that requires dimensions to be measured carefully. Measurements must done with a micrometer, with go-no gauges, jigs and fixtures, or calibrated machines, never 'judged by eye'.

Old-fashioned fitting is how I work. The system uses the work itself as a series of gauges, each part being trimmed to fit into another. Accurate measurement isn't required, and stuff can be judged by feel. Fitting works in any system of measure, Uncouth can believe I'm lying if he wants, but I do the same as he does in metric.

Fitting is great for home-workshops and repair work, but it fails miserably for production work. First problem, is that fitting is hideously expensive because the work is both skilled and labour intensive. Chaps who do it burble on about 'quality', but never mention productivity, which is rock-bottom. Worse, fitted components aren't interchangeable. If the parts from 20 PottyMill engines were scrambled and re-assembled, it's unlikely that any of the engines would work, and those that do are luck rather than engineering.

Interchangeability is achieved by setting tolerances and knowing for certain that all the parts are accurately machined to fit together by design. Parts made at different times and places can be brought together and assembled without 'judging slop with a slip'. If that's necessary, something has gone horribly wrong.

Fortunately interchangeability is rarely important in home-workshops. It's why I don't own any slip gauges, or anything better than a 0.01mm micrometer. I've even experimented with making stuff using plain calipers as comparators only. Works surprisingly well with care. The method knows nothing of 'thou': it's all done by feel.

Perhaps the worst feature of Imperial is it seems cuddly friendly at first. But first contact is misleading. It's rather like discovering the house of your dreams is built over a 200 fathom deep mineshaft full of chemical waste. All you have to do is ignore a few cracks in the walls and an occasional hint of Phosgene in the kitchen.

My point is purchasers might do better to buy an equally good house that doesn't have faulty foundations. Even if you personally don't understand a survey full of weird technical terms!

Always good to tilt a debate on it's head. As Duncan says, none of the world's metric users sees any advantage in Imperial. The only reason it's used is to supply legacy markets, almost never for new design. Imperial is gradually fading, even in the US.

Like it or not, Imperial measure is obsolescent. It's damaging to to foist it on the next generation. Don't stuff up the kids with Imperial, or any other old friends, when something better is available or time has marched on.

Dave

Sorry Dave have to disagree

It's damaging to to foist it on the next generation. why have you asked them ? We have to 2 young members in my club who are more than happy to work in imperial

H

[BaldricParticipant @baldric]

Posted by Dave Halford on 04/03/2023 10:51:38:

Posted by samuel heywood on 04/03/2023 01:03:50:

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.

B&Q still sell 8×4 sheets of ply etc disguised as metric 2.44M x 1.22M so they have gone metric sort of.

PS Video 2000 was the best system with auto tracking.

Edited By Dave Halford on 04/03/2023 10:52:42

I found out the hard way that whilst.ply is actually imperial, plasterboard is metric, so it didn't match my spacing of joists.

[BaldricParticipant @baldric]

Posted by Dave Halford on 04/03/2023 11:22:53:

There's also the world of telecom's equipment.

American 19" wide racks use a height unit of an U which is 1.75" or 44.5mm by 482mm wide

European ETSI 21" wide racks use a height unit of an SU which is 25mm or 1" ish by 533mm wide.

So what should be Metric isn't always.

I was not aware of that, I wonder why someone decided.to create a new standard when it means a lot of equipment won't fit. I am sure you can get narrow 19" racks, that just leaves less room for cables down the side of equipment.

[Frances IoMParticipant @francesiom58905]

just replaced my kitchen radio with a new, made-in-China, undershelf DAB model from Lidl – the measurement for placing the screws so it lines up with the shelf was 31.5mm – aka one and a qtr inches ! – so much for metrication

Edited By Frances IoM on 05/03/2023 19:05:09

[SillyOldDufferModerator @sillyoldduffer]

Posted by Harry Wilkes on 05/03/2023 18:23:14:

Posted by SillyOldDuffer on 04/03/2023 10:40:16:

Posted by UncouthJ on 03/03/2023 19:40:55:

Posted by Nicholas Wheeler 1 on 03/03/2023 18:32:39:

Posted by UncouthJ on 03/03/2023 15:49:00:

…

…

…

…

Perhaps the worst feature of Imperial is it seems cuddly friendly at first. …

Like it or not, Imperial measure is obsolescent. It's damaging to to foist it on the next generation. Don't stuff up the kids with Imperial, or any other old friends, when something better is available or time has marched on.

Dave

Sorry Dave have to disagree

It's damaging to to foist it on the next generation. why have you asked them ? We have to 2 young members in my club who are more than happy to work in imperial

H

Really? Even after slugs were explained? They must be very bright…

Dave

[JasonBModerator @jasonb]

So long as the male population continue to measure one tool that is always easy to hand in inches there will always be a use for imperial

[phillip gardinerParticipant @phillipgardiner]

Baldric 4×2 in Australia was always3 7/8 x1 7/8 of the saw unless it had to be dressed then it was 4×2

[UncouthJParticipant @uncouthj]

Posted by JA on 04/03/2023 09:44:35:

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

And BUSTED! 😂🤣

Glad someone got it!

It's a pointless argument and always has been. As I said before, just a fun biannual dust up…

Edited By UncouthJ on 05/03/2023 22:01:42

[NealebParticipant @nealeb]

Like many others here, as a pragmatic engineer (is that a tautology?) I use whichever is easier at the time. My loco model drawings are imperial, covered in fractions. Sometimes I use a scan of the original in the workshop, sometimes a drawing from the 3D CAD model which is in mm. If the former, it probably has decimal equivalents scribbled on it because my DROs are metric/imperial agnostic but they don't do fractions! The only other problem area is screwcutting. My imperial Myford made cutting imperial TPI threads easy. However, cutting metric "pitch" threads on a metric lathe often means swapping the TDI drive gear, and you need three of those to cover the usual range of threads on my machine.

[Bdog507Participant @bdog507]

Good morning all.

It's funny how the UK decided to go metric in 1965 & we still haven't got there. Lots of things are still sold in imperial amounts but expressed in metric. Beer in 568ml bottles and so on.

Those of us above a certain age were taught in imperial. It was all feet & inches, pounds & ounces for me at school. However, most of us have learnt to use metric. I actually prefer it when I'm machining. Not least because my lathe has metric dials. My mill has imperial dials but I use the DRO in metric.

It amuses me when I use an imperial measurement when speaking to a younger customer, & they claim not to know any of 'that old stuff'….I ask them how tall they are, & invariably they'll day 5' 9" or whatever. Rarely do they express their height in metric form…….Don't know that old stuff eh!

I don't think certain imperial units are going anywhere soon. Take the horsepower for example. Then again saying "My bike has 100 hp at the back wheel" sounds better down the pub than "My bike has 74.6kw at the back wheel" might be the reason for the horsepower lingering.

Cheers.

Stewart.

[Martin KyteParticipant @martinkyte99762]

The thing you are measuring is not intrinsically metric or imperial, your choice of measurement systems is. Horsepower is not imperial neither is it metric but based on the output of a horse. Actually the rate at which said horse could raise a weight of 550 lbs or 250kg through a fixed distance of one foot in one second. It may perhaps be better described as an equine system of measurement if you really want to ascribe it to anything.

regards Martin 🥴

[Bdog507Participant @bdog507]

Hmmmm! Devil's advocate time 😁😁

 

I believe James Watt's original calculation was indeed 550 lb/sec or rounded up to 33.000 ftlb a minute. It became known as the mechanical or imperial.horsepower….but there's this thing known as a metric horsepower or PS which is slightly smaller at circa 542 lb/sec or circa 735 watts.😄😄

 

Cheers.

 

Stewart.

Edited By Bdog507 on 06/03/2023 14:54:23

[Harry WilkesParticipant @harrywilkes58467]

Posted by SillyOldDuffer on 05/03/2023 20:39:47:

Posted by Harry Wilkes on 05/03/2023 18:23:14:

Posted by SillyOldDuffer on 04/03/2023 10:40:16:

Posted by UncouthJ on 03/03/2023 19:40:55:

Posted by Nicholas Wheeler 1 on 03/03/2023 18:32:39:

Posted by UncouthJ on 03/03/2023 15:49:00:

…

…

…

…

Perhaps the worst feature of Imperial is it seems cuddly friendly at first. …

Like it or not, Imperial measure is obsolescent. It's damaging to to foist it on the next generation. Don't stuff up the kids with Imperial, or any other old friends, when something better is available or time has marched on.

Dave

Sorry Dave have to disagree

It's damaging to to foist it on the next generation. why have you asked them ? We have to 2 young members in my club who are more than happy to work in imperial

H

Really? Even after slugs were explained? They must be very bright…

Dave

Of course they are give them a drawing and they can work in either imperial or metric ! Also I would suggest one needs to be bright to be a model engineer

H

[Martin KyteParticipant @martinkyte99762]

Posted by Bdog507 on 06/03/2023 14:53:52:

Hmmmm! Devil's advocate time 😁😁

I believe James Watt's original calculation was indeed 550 lb/sec or rounded up to 33.000 ftlb a minute. It became known as the mechanical or imperial.horsepower….but there's this thing known as a metric horsepower or PS which is slightly smaller at circa 542 lb/sec or circa 735 watts.😄😄

Cheers.

Stewart.

Edited By Bdog507 on 06/03/2023 14:54:23

Yes but my point was the horsepower unit is based on the horse not the system of measurement. The pound is defined by the imperial system of measurement and the metre on the metric system. A horse is just a horse.

regards Martin

[Paul McDonoughParticipant @paulmcdonough43628]

I am inclined to agree that for many of us either system is fine, where it struck a chord with me is that once upon a time my old man would have had imperial drill sets, I grew up with this, until opening the plans for my new project it haden't occurred to me that I might still need such a drill set! So for me, a beginner returning to the fold after 40+ years away this is an irritation, not to mention the set of BA taps and dies and likely an imperial set for small pipe fittings yet to come.

I see no need to impose this on the next generation, so ideally it would end at some point, although the key reason given for this, the reuse of old imperial plans doesn't seem to be abating any time soon.

Apologies for triggering this slightly awkward debate, I was genuinely curious as to why my seeming new steam engine kit which is made from stock materials and has no castings was dimentioned in imperial? And now i half know! :0)

[Martin KyteParticipant @martinkyte99762]

The use of old plans is pretty much locked in. Suppliers are not going to change anything, where would be the profit and who would pay for the redesign. Even drawing errors are never corrected either due to copyright or changing a design means the supplier is at fault if it’s wrong. This is after all an amateur pastime. There may be a few new engine designs around and similarly with clocks but the output is small and unlikely to dominate anytime soon.

That said Martin Gearing’s Grasshopper Beam Engine currently serialised in ME is a metric design so there you go.

regards Martin

[duncan webster 1Participant @duncanwebster1]

Posted by Martin Kyte on 06/03/2023 15:00:34:

Posted by Bdog507 on 06/03/2023 14:53:52:

Hmmmm! Devil's advocate time 😁😁

I believe James Watt's original calculation was indeed 550 lb/sec or rounded up to 33.000 ftlb a minute. It became known as the mechanical or imperial.horsepower….but there's this thing known as a metric horsepower or PS which is slightly smaller at circa 542 lb/sec or circa 735 watts.😄😄

Cheers.

Stewart.

Edited By Bdog507 on 06/03/2023 14:54:23

Yes but my point was the horsepower unit is based on the horse not the system of measurement. The pound is defined by the imperial system of measurement and the metre on the metric system. A horse is just a horse.

regards Martin

Ah but, if you kitted out said horse with a space suit, it would be able develop more than one horsepower on the moon, as the work required would be less in zero gravity. Confusing mass and force is just one failing of the imperial system. However, we'll never convince die hard imperialists, their system can be made to work using a plethora of conversion factors (and a lot of concentration) and they are familiar with it.

[Dave HalfordParticipant @davehalford22513]

Posted by Baldric on 05/03/2023 18:34:28:

Posted by Dave Halford on 04/03/2023 11:22:53:

There's also the world of telecom's equipment.

American 19" wide racks use a height unit of an U which is 1.75" or 44.5mm by 482mm wide

European ETSI 21" wide racks use a height unit of an SU which is 25mm or 1" ish by 533mm wide.

So what should be Metric isn't always.

I was not aware of that, I wonder why someone decided.to create a new standard when it means a lot of equipment won't fit. I am sure you can get narrow 19" racks, that just leaves less room for cables down the side of equipment.

Well, you can get 21 to 19 inch adapters should you have mixed equipment. Going the other way is impossible as you can't remove the outside edge blades/cards

[Martin KyteParticipant @martinkyte99762]

Well one sixth g but I’m sure you meant that.

The force/mass issue is interesting in as far as it illustrates the locality of imperial measurements and the universality of SI units. Various fudges get around the use of the same unit to define both mass and weight and really one should specify pounds mass or pounds weight in standard earth gravity which is cumbersome to say the least.

As I’ve said before I quite like imperial linear measures for ME even fractions and number and letter drills as I feel connected to the history of the hobby. But that’s just me and outside that limited sphere I reach for SI every time.

Cheers Duncan

regards Martin

Edited By Martin Kyte on 06/03/2023 17:11:34

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