Metrication of models

[SillyOldDufferModerator @sillyoldduffer]

Posted by JasonB on 04/10/2019 18:49:33:

… who wants to try and machine a part that may have been 1 3/8" to 34.925 long when 35mm is a much simpler figure …

Not sure that one holds water because most imperial machines and their owners work in thou, not fractions. 1 3/8" is OK because it happens to work out neatly to 1.125". Plenty of other common inch fractions are less cooperative, for example: 1/3" is 0.333333 recurring, 3/16 is 0.1875", and 7/64 ie 0.109375". That inch fractions don't always translate neatly to thou doesn't bring Imperial workshops to a shuddering halt, and neither should 34.925mm.

Personally I find it best to avoid fractions in both Imperial and Metric. I wonder when the last professional mechanical engineering drawing used fractions? 90 years ago perhaps. My 1907 ICS Book insists measured or gauged dimensions be expressed to 3 places of decimals, fractions forbidden. It also explains how to design to the nearest 1/64th of an inch, this being the accuracy expected of most metalwork before thou accuracy and tolerances became the norm. 1/64" is an eyesight limit and no-one uses the method now because we all have calipers, micrometers and DROs. Time marches on.

Dave

[JasonBModerator @jasonb]

Posted by SillyOldDuffer on 04/10/2019 20:48:14:

1 3/8" is OK because it happens to work out neatly to 1.125"…………………………..

………………………Personally I find it best to avoid fractions in both Imperial and Metric.s on.

Dave

I can see why

[SillyOldDufferModerator @sillyoldduffer]

Posted by JasonB on 04/10/2019 20:51:43:

Posted by SillyOldDuffer on 04/10/2019 20:48:14:

1 3/8" is OK because it happens to work out neatly to 1.125"…………………………..

………………………Personally I find it best to avoid fractions in both Imperial and Metric.s on.

Dave

I can see why

And I used a calculator!!!

ARGHH….

[Anonymous]

Posted by SillyOldDuffer on 04/10/2019 20:57:32:

And I used a calculator!!!

Oh my word; eighths and sixteenths in decimal should be instant recall!

I still use 64ths, albeit not explicitly. If I'm machining a spigot that is, say, 3/8th long I'll hold a rule on the toolpost on the first pass and knock off the feed just before 3/8". The I'll turn the spigot to the correct diameter and finally take thin cuts off the shoulder. After each thin cut I put the rule on the work, resting against the shoulder, and if the end of the spigot is within a lines width of 3/8" on the rule that's good enough. If better accuracy is needed I'll dig out the depth micrometer.

Andrew

[Dave Smith 14Participant @davesmith14]

Posted by SillyOldDuffer on 04/10/2019 20:48:14:…

Personally I find it best to avoid fractions in both Imperial and Metric. I wonder when the last professional mechanical engineering drawing used fractions? 90 years ago perhaps.

Dave, a lot later than you think. I volunteer on the Mid Hants at Ropley. The 'BR' not Southern drawings done at Ashford in the 50's for Spam Can tenders are all in fractional inches, with a few odd dimensions mainly diameters in decimal. As an aside in 40 years of professional engineering, these drawings are some of the worst I have ever come across.

Dave

[Bill PudneyParticipant @billpudney37759]

I was a contract drafty at a machinery company in the early 70s. They used fractional dimensions on casting drawings, decimal dimensions on fabricated and machining drawings. It made some sort of sense at the time!!

I started work for the MoD (N) in the mid 70s and had the privilege of working on what I was told was the first "metric" ship built for the Real Navy, (the Type 22 class of frigates).

cheers

Bill

[Brian GParticipant @briang]

Imperial may be dead in manufacturing drawings, but ten years ago I was still drawing components with 7.2mm holes in 1.6 x 1.6 x 19mm angle.  Good practice for 16mm/ft scale models where a component 1/8" Dia x 64mm can turn up on a drawing.

To be fair, the metric system has only been fully legal in the UK since the 1880s, and we don't like to rush into these things.

Brian

Edited By Brian G on 05/10/2019 08:51:35

[JasonBModerator @jasonb]

Posted by Brian H on 04/10/2019 19:52:37:

If you are modelling a prototype that was built in metric then use metric and if (like me) you are modelling a prototype that was made in Imperial then use Imperial.

Those with no background in imperial will also find it hard to understand scales like 3" and 6" but may grasp the idea of 1/4 or 1/2 scale.

They are more likely to be used to the preferred metric scale of 1:2, 1:5, 1:10, etc so may choose to make a traction engine at say 1:5 which in all probability would like imperial loco builder do be done at 5mm to the inch or 1:5.08.

Or they may go the way of figure and railway modellers as mentioned above and use a mm/ft or inch ratio. so that old imperial 3" traction engine would not be too difficult to build using 8mm/1"

The comment that it is hard to find metric stock really only applies to small lengths bought through UK ME suppliers. Trade suppliers will carry more metric than imperial and you would have a job to get imperial materials in mainland Europe or many other countries that have grasped the metric system.

[duncan webster 1Participant @duncanwebster1]

Posted by Peter Layfield on 04/10/2019 16:37:05:

I thought that when we left the E.U. we were going to revert back to imperial measurements in line with

the US of A and the rest of the world

In your dreams, like we'll be reverting to pounds shillings and pence as well. Only old f*rts like us understand imperial, and I for one much prefer metric, just give it a go, it's easy

[John HinkleyParticipant @johnhinkley26699]

Like many on this forum, I was educated in the feet and inches era, when "times tables" were learnt by rote and were handily available on the back cover of our exercise books, along with conversions of rods, poles and perches. When we moved to France, I had to decide whether to make my workshop metric or stay Imperial. I chose metric. A couple of year ago, and now back in the UK, I purchased a Worden T & C grinder kit from Hemingway and was surprised to see that the drawings contained a mix of Imperial and metric, fractions and decimal. I decided to convert it all to metric and redrew all the drawings. It took a long, long, time. I offered them to Hemingway, but they declined the offer. Sadly, I lost the lot in "the big hard drive crash of 2018". I haven't had the urge to do them again.

John

[Bruce EdneyParticipant @bruceedney59949]

I'm currently metricfying (is that a word and have I spelt it right?) the Farmboy Hit & Miss engine drawings. I started off just doing a 1" = 25.4mm conversion but ended up with some odd metric sizing and I still had to deal with standard stock sizes. Lots of dimensions can and have changed and it is a lot of work to ensure parts still work together.

Here's a question though: Once I am finished and built it are the metric drawings I have created now mine to sell or are they still subject to the original copyright?

With regards to Metric fasteners. If you can't source them from your own country then you can certaining get them from Aliexpress easily enough.

Cheers

Bruce

[HOWARDTParticipant @howardt]

Bruce. Metricating does not change copyright. I believe a design has to be substantially changed to create a new copyright. Consider people like Dyson etc and their copyright infringement cases.

[DMBParticipant @dmb]

Hi All,

I sit here after a hard day at the track, chuckling at the fresh can of worms I've opened, to fit alongside JA's!

I am the " wrong" side of 70 but feel comfortable with Imp. or metric, since I had both to contend with at school. At the time, couldn't see the point of this new – fangled decimal system except in Science lessons where it proved to be SOOOO much easier to use.

Duo-decimal currency, "2 farthings = a ha'penny, 2 ha'pennies = a Bob, sorry 1 shilling" and so on.

As mentioned above, rods, poles, perches, chains, quarts, 8 pints = 1 gallon, 112 lbs = 1 cwt. What a load of old medieval crap that belongs in some countryside museum. Thank goodness it's all going. I am now however, very grateful to my school for teaching me both systems so I can easily use which I choose. It's simply so lovely to just shift a decimal point when doing mental arithmetic. Still difficult to visualise some things, e.g., I have seen pictures of new cars dimensioned in thousands of mm! What you absolutely must not do is try to convert due to the extremely awkward equivalents. Must choose and stick to the one system throughout a whole build project. Enough drawing errors without an exponential increase caused by conversions followed by rounding off dimensions.

 

Edited By DMB on 05/10/2019 22:47:56

[DMBParticipant @dmb]

The world moves on at what seems like an exhaustingly quicker pace. Or am I really slowing up at an alarming rate? Ha, ha!

All of you older forumites have experienced the tsunami of modern technology, same as me and some have picked up the baton and run with it faster than others. I look at things and think, can I make good use of this or that, or not? E.g., much better to have mobile in pocket than have to walk 1/2 mile to BT phone box and then find it smashed up and out of order. I have taken on board small things like led ring light for vert. mill, electronic rev counter for mill, lathe, bench drill. Dro s for mill. VFD on lathe. Mitutoyo elec. calipers. I just about cope with 'puters sometimes with a little help from my professional programmer nephew but to try to use it for 3D modelling is a step too far. While I would be struggling to master that, I would be losing a lot of time to do other things and life is rapidly getting shorter! Don't tell me that it would eventually save me a lot of time. I cannot see any great use for it for me. Mechanical stops and Dro s are perhaps a sort of halfway house but which I can make immediate good use of.

It all depends upon what you want to do.

[DMBParticipant @dmb]

Lease EU and revert back to Imperial? I hope not. We will probably become more aligned with USA for trade, using Imp for some types of business and metric to trade with the rest of the world. Just wish Parliament would obey a referendum result instead of keep trying to kick it around til they lose it. What's the point of having one if MPs want to ignore it? Get it sorted, move on and complete the metrication process which has also gone off at half- cock. Let's have some real progress and leave us old codgers to continue playing about with BA and BSF! Sod it, I'm  tired, it's late, cat out on nightly prowl and I'm off to bed.

Edited By DMB on 05/10/2019 23:28:34

[Enough!Participant @enough]

Posted by DMB on 05/10/2019 22:45:04:

2 ha'pennies = a Bob, sorry 1 shilling"

Huh?

[Anthony KnightsParticipant @anthonyknights16741]

When I was at secondary school we were taught using both systems. Applied mathematics was a nightmare with foot pounds, Briish Themal Units etc. Loved Physics where it was all grams and centimeters. That's all changed, as it is now the MKS system which does produce some stupidly large or small standard units which don't relate to every day useage. Pascals spring to mind.

I am happy using Imperial or metric, although imperial is used mainly for woodwork (sheet material still 8ft x4ft) while metric gets used for metal. I still need to mentally convert large mm measurements to feet in order to visualise sizes.

Edited By Anthony Knights on 06/10/2019 09:23:21

[DMBParticipant @dmb]

Bandersnatch, I do know better, put it down to tiredness error,

but,

I now know you read it!

Seriously, what a hideous system of value measurement. I think it was because so many everyday items had such a low price, e.g., loaf of bread one old penny. Blame inflation for making system look so outdated. Remember one of my secondary school teachers saying that this age would go down in history as the age of change just for the sake of it. He did appear to be nearing the end of his career. I find it amazing how quickly I adapted to the then new decimal currency but still see, say 1.5mm and automatically try to convert it to 60 thou as an approximate equivalent to be able to visualise that size. Soooo annoying.

[DMBParticipant @dmb]

Anthony,

This is the stupidity, 8ft long board easily visualised but if "they" go and "metricate" that to 2,400mm or even worse, 2,440 or 2,450, that would be awful. Just like the 19ft new car quoted as being 57,912mm long! I would like to see my restricted to less than 1m, then go on to use say 1.4m or 2.9m or whatever, applicable to all industries, "no ifs, no buts."

[FMESParticipant @fmes]

This topic never ceases to amaze me at the amount of discussion it generates.

I think I have mentioned before, that having previously taught EDF Energy apprentices in the age range of 16 to 22 we have had to spend some time teaching imperial measurement, mainly due to the fact that the majority of nuclear reactors currently operating in the UK ar indeed imperial, and will continue to be so for the future as the decomissioning life still has to be addressed with repairs and replacements of the non-metric variety.

In addition the majority of older and still in comission American ships and aircraft,,still require a knowledge of the imperial system.

I refuse point blank to 'metricate' a set of drawings as the possibility of error is high and believe whole heartedly that for steam in particular, everything should be imperial. – just my point of view.

Incidntally, when introducing the EDF apprentices to Imperial measurement ( and all of the little engines they made in our workshops were on imperial drawings) , it only took them about half a day to grasp the concepts and by the end of the day working happily with supplied imperial drawings.

Regards.

[JasonBModerator @jasonb]

Posted by DMB on 06/10/2019 11:49:09:

Anthony,

This is the stupidity, 8ft long board easily visualised but if "they" go and "metricate" that to 2,400mm or even worse, 2,440 or 2,450, that would be awful.

Would be great if they metricated it to 2400mm, then the plasterboard on the underside of your flat roof would match the ply on top and the standard 400cts of joists.

[Nick Clarke 3Participant @nickclarke3]

The need for exact standard sections becomes less of an issue if the design process is thought through. Where size is not needed to be exact many designers appear to have said 'chuck a piece of 5/32" bronze bar etc when what they needed was a piece of metal large enough to finish to the desired size, more or less. Also with older designs I suspect designers did not want to inflict unnecessary machining down to size on hobbyists with limited machining facilities. To the end of his life LBSC wrote about 'those lucky enough to have a milling machine' when today far more people either possess one or have access to one through a club.

What I am trying to envisage is the designer thinking of 1.2" but making it 1 1/8" for simplicity and today needing to use 30mm for convenience. Neither of the two alternatives are accurate to the original idea, but both work and if you want accurate – today you can mill it!.

One interesting thought about measurements is regarding copper sheet. It used to be thought that 10g, for example, was a replacement for 1/8" being a few thou thicker. 3mm is about 10 thou thinner than 10swg But US 10g (B&S) is thinner again. If we are buying copper sheet or tube with our import streams focused more across the Atlantic than into Europe which will we be getting in the future??

All will probably be within any reasonable safety factor, but several published boilers with 'grandfather rights' as established designs have been questioned in today's world and I don't think this will help.

[JasonBModerator @jasonb]

Posted by FMES on 06/10/2019 12:25:01:

 

I refuse point blank to 'metricate' a set of drawings as the possibility of error is high and believe whole heartedly that for steam in particular, everything should be imperial. – just my point of view.

Maybe if you are building an old Loco but what about someone wanting to build say a flash steam boiler and high speed engine or a turbine, can't see any reason why they would have to be imperial, just my view.

Or what about a steam engine like this which I know a couple of people are currently building, Originally designed in metric and built in metric so why should it only be modelled in imperial? Or is steam only a British thing.

Edited By JasonB on 06/10/2019 15:04:33

[SillyOldDufferModerator @sillyoldduffer]

Posted by FMES on 06/10/2019 12:25:01:

This topic never ceases to amaze me at the amount of discussion it generates.

…

In addition the majority of older and still in comission American ships and aircraft,,still require a knowledge of the imperial system.

…

Regards.

Which ten years ago caused serious delays when Boeing was developing the 787 airliner. Not funny when you design an airliner in the US while relying on keeping the price competitive by having much of it made more economically abroad and it turns out the rest of the world doesn't understand US Customary units! A lot of expensive mistakes were made…

I wonder how many British engineering firms bit the dust due to upsetting export customers by failing to metricate? Unfortunately, most customers interested in buying British machines care absolutely nothing about heritage units like inches or Whitworth's genius (Sir Joseph died in 1887). What they do want is affordable equipment that's easy to maintain. Like it or not metric equipment has the edge in metric countries.

Teaching students to work from imperial drawings in an afternoon glides over Imperial's secret shame. On their own inches, pounds, miles, and pints etc are familiar and even cuddly. Perhaps that's part of the problem. The trouble starts when Imperial is applied to physics and those incoherent Imperial units have to work together. The full awfulness of the Foot-Pound-Seconds system doesn't really bite until serious engineering is afoot which rarely happens in the average home workshop. Imperial measure may seem friendly to chaps skimming the surface, but it's pure treacle for anyone doing proper engineering rather than knocking stuff up from someone else's design.

No-one should be allowed to support imperial until they can explain Slugs, Biot-seconds, Candles, the various definitions of 'pound', and all those strange conversion numbers that pop up in formulae only because Imperial is internally inconsistent. Definitely not allowed to lobby in favour until the difference between FPS and Technical FPS is understood, and a working knowledge of British vs USA FPS would be an advantage. Man-in-pub and woodworkers need not apply.

Anyone who thinks Imperial does a good job has only skimmed the surface. Metre-Kilogram-Seconds is more suitable because it's simpler. Apart from backward compatibility, is there a logical reason for sticking with Imperial measure in future? I can't think of one.

Dave

[TrickyParticipant @tricky]

Posted by SillyOldDuffer on 06/10/2019 15:03:27:

Posted by FMES on 06/10/2019 12:25:01:

This topic never ceases to amaze me at the amount of discussion it generates.

…

In addition the majority of older and still in comission American ships and aircraft,,still require a knowledge of the imperial system.

…

Regards.

Which ten years ago caused serious delays when Boeing was developing the 787 airliner. Not funny when you design an airliner in the US while relying on keeping the price competitive by having much of it made more economically abroad and it turns out the rest of the world doesn't understand US Customary units! A lot of expensive mistakes were made…

I wonder how many British engineering firms bit the dust due to upsetting export customers by failing to metricate? Unfortunately, most customers interested in buying British machines care absolutely nothing about heritage units like inches or Whitworth's genius (Sir Joseph died in 1887). What they do want is affordable equipment that's easy to maintain. Like it or not metric equipment has the edge in metric countries.

Teaching students to work from imperial drawings in an afternoon glides over Imperial's secret shame. On their own inches, pounds, miles, and pints etc are familiar and even cuddly. Perhaps that's part of the problem. The trouble starts when Imperial is applied to physics and those incoherent Imperial units have to work together. The full awfulness of the Foot-Pound-Seconds system doesn't really bite until serious engineering is afoot which rarely happens in the average home workshop. Imperial measure may seem friendly to chaps skimming the surface, but it's pure treacle for anyone doing proper engineering rather than knocking stuff up from someone else's design.

No-one should be allowed to support imperial until they can explain Slugs, Biot-seconds, Candles, the various definitions of 'pound', and all those strange conversion numbers that pop up in formulae only because Imperial is internally inconsistent. Definitely not allowed to lobby in favour until the difference between FPS and Technical FPS is understood, and a working knowledge of British vs USA FPS would be an advantage. Man-in-pub and woodworkers need not apply.

Anyone who thinks Imperial does a good job has only skimmed the surface. Metre-Kilogram-Seconds is more suitable because it's simpler. Apart from backward compatibility, is there a logical reason for sticking with Imperial measure in future? I can't think of one.

Dave

Does that mean nobody should use metric unless they understand ALL the metric units that exist?

I was taught cgs at school but I can work in metric or imperial but I do not know all the units, only those I need.

Richard

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