Forum sponsored by:
Forum sponsored by Forum House Ad Zone

Why is the world of model engineering still imperial?

All Topics | Latest Posts

Search for:  in Thread Title in  
Martin Kyte04/03/2023 09:59:43
avatar
3445 forum posts
62 photos

Perhaps not quite back to the flood but certainly the French Revolution and Napoleon.

:0)

Martin

Michael Gilligan04/03/2023 10:08:26
avatar
23121 forum posts
1360 photos
Posted by Martin Kyte on 03/03/2023 20:43:37:

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.

.

+1

… or +25.4 for that matter

MichaelG.

.

Edit: __ of course, the ‘missed opportunity’ was when they failed to make the ‘exact’ conversion 1: 25.6

Edited By Michael Gilligan on 04/03/2023 10:15:13

Graham Titman04/03/2023 10:11:18
avatar
158 forum posts
28 photos

I cannot understand why this keeps coming up if you do not like imperial convert it to metric no problem easy. Where i worked in the seventies the companey took all the grants and converted the drawing office to metric one small problem EVERY machine was imperial cheap way out every machine had a calculater and no winging for weeks after we just sat there for a few minutes and played with  25.4 to three decimal places and got on with it.Jobs were done

Edited By Graham Titman on 04/03/2023 10:12:46

John Abson04/03/2023 10:23:35
22 forum posts

I've noticed an increasing move in ME to use metric dimensions. It makes procurement of standard materials and tools easier and in some cases cheaper, in the UK at least. DROs especially on milling machines - 'once you've used one, you'll never go back' seems common - simply switch between metric and inch. Even my digital calipers do the same.

Fits and tolerances really don't come into it, once you've made the mental adjustment (OK, some people will never make that jump, but that's not because of the measuring system base IMO).

I spend a lot of my life restoring and making parts for old pipe organs, all made to inch dimensions. Makes a lot more sense to use inch on those, but metric on more recently built instruments. Errors are less and its easier to measure in the respective measuring system base used on the original. Likewise, when building a model designed in inches, one is better sticking to inches.

I was recently 'given' a Bosch tape measure as a promotional giveaway. Functionally it's the best tape measure I've ever owned (and I've lost dozens and found a few ) but is only marked in metric. After about half a day, I felt liberated from the tyranny of the inch!

/J

Edited By John Abson on 04/03/2023 10:24:39

JasonB04/03/2023 10:25:48
avatar
25215 forum posts
3105 photos
1 articles

As I said before simply doing the mathmatical calculation is not really a proper conversion to metric that 12.7 x 0.623pitch tap will be hard to find so you are only changing numbers not physical parts and associated tooling.

I suppose most people put up with it and those that do change a set of drawings to a full metric conversion just tend to keep them to themselves rather than make them available to others. Probably not helped by the Likes of Stuart's who are often suggested as the source for "your first casting set" who supply the materials and fixings too. Most buying a kit will tend to buy BA and make use of the supplied material and now on the slippery slope will slide into the imperial/BA way it has always been done. If they just supplied castings then I bet there would be a lot more metric 10Vs about as the drawings are out there.

SillyOldDuffer04/03/2023 10:40:16
10668 forum posts
2415 photos
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

Michael Gilligan04/03/2023 10:50:57
avatar
23121 forum posts
1360 photos
Posted by John Abson on 04/03/2023 10:23:35:

[…]

After about half a day, […]

.

0.5 day in Metric angel

MichaelG..

Dave Halford04/03/2023 10:51:38
2536 forum posts
24 photos
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 wink, 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. sad

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 8x4 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

John Abson04/03/2023 10:58:30
22 forum posts
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 angel

MichaelG..

Nice one!

However there are 24 hours in a day so time is definitely Imperial based (yay!!) John Harrison was, after all an Englishman - oh crikey, are degrees of latitude and longitude metric or imperial??? (think I'll just go and hide!)

Dave Halford04/03/2023 11:22:53
2536 forum posts
24 photos

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.

Martin Kyte04/03/2023 11:42:14
avatar
3445 forum posts
62 photos
Posted by John Abson on 04/03/2023 10:58:30:
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 angel

MichaelG..

Nice one!

However there are 24 hours in a day so time is definitely Imperial based (yay!!) John Harrison was, after all an Englishman - oh crikey, are degrees of latitude and longitude metric or imperial??? (think I'll just go and hide!)

Babylonian actually.

Regards Martin

Clive Steer04/03/2023 11:48:48
227 forum posts
4 photos

I'm rather late to this subject but it is not only model engineering that is Imperial as electronic components are often on Imperial 0.1 inch pitch. I'm happy to work in either measurement system but the whole concept of fractions makes arithmetic excruciatingly difficult and rather like doing sums using Roman numerals and a recipe for error.

CS

duncan webster04/03/2023 11:55:10
5307 forum posts
83 photos

Just to be pedantic (who me?) I think 24 hour day was from ancient Sumeria via ancient Egypt, it is 60 minutes in an hour that is Babylonian. Bit difficult to claim this as imperial, and it's fairly widespread in the rest of the world. Use of 12 is also Sumeria, it comes from 4 fingers each having 3 knuckles, then you have 12 hour day and 12 hour night.

As regards tolerances, when Ford were asked to consider making Merlins, they stated they couldn't work to RR, tolerances. Not because they were too tight, RR used selective assembly and fitting when building engines, for mass production you need much tighter tolerances so thar you just pick up parts and assemble them, no faffing about.

Mike Poole04/03/2023 12:29:52
avatar
3676 forum posts
82 photos

Our time and motion men used stop watches that used centiseconds, it made it much easier to add the individual parts of a process together to get an answer in seconds.

Mike

Another JohnS04/03/2023 12:47:14
842 forum posts
56 photos
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 Wheeler04/03/2023 13:12:20
1227 forum posts
101 photos
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 angel

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

Bantam Bill04/03/2023 13:42:50
13 forum posts
1 photos

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

Nick Wheeler04/03/2023 14:02:31
1227 forum posts
101 photos
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 haysom04/03/2023 14:45:46
avatar
165 forum posts

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 Dayman05/03/2023 18:11:39
2356 forum posts
47 photos

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.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

 

Donate

donate