pmsl

The main problem is our standardising on the mm as the base. It gives such large figures that are difficult to visualise and imply an accuracy that isn't attainable in all circumstances. As others have said, working using imperial gives the level of accuracy with the measurement. I was taught never to quote more places of decimal than is necessary for the accuracy required. When I see figures in mm, I assume we need to work to the nearest 0.5mm - in wood???

In metric, we now have the "metric foot" of 300mm which means you get short changed - and leads to errors in conversion...

We should have done what is used in France, and probably other metric countries - use metres and decimals thereof for large measurements, cm and decimals for medium accuracy and only mm and decimals for high accuracy (ignoring the scientists). They choose the appropriate base measurement rather than having everything in mm. When I buy a ruler in France, the printing is appropriate for the length. (and I bought wood in metre lengths) You also still come across people using "pouce", which is about an inch...

Reply to
JohnDW
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That's more of an industry standardisation thing though.

The normal ones are called right handed because you hold the cassette in your right hand, but I agree with you.

For measurements up to 600mm I use a Starrett metric rule which can be used both ways.

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finer work, the Incra ones are good

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Reply to
Andy Hall

That depends on use and application and for that matter, equipment in use. I would argue that the metric system actually makes that easier because one can use significant figures.

For example, if one thinks about cutting materials to length, it might be reasonable for a project to cut a 2000mm piece to an accuracy of

2mm, whereas a 200mm piece might need to be cut to 0.2mm for an accurate fit.

As I already mentioned, it's very easy to apply rounding. In imperial, that involves a lot of fiddling with numbers.

That makes no sense at all. It does no such thing.

I agree. Standard engineering training.

It may well be. I often work to +/- 0.2mm in hardwoods, better if I can do it.

You only get short changed if you continue to think in the deprecated old units. As soon as you work entirely in one unit, the issue goes away.

That hardly matters because if you are buying wood from a merchant , lengths are inaccurate anyway

Reply to
Andy Hall

I was trying to explain this concept to my son last night, helping him with his chemistry homework. They'd done a practical in which they'd been measuring the time taken for different lengths of Mg ribbon to dissolve in HCl. His results were something like:

1 cm: 45.23 s 2 cm: 76.18 s 3 cm: 65.03 s 4 cm: 90.67 s

Still don't think he gets it though!

David

Reply to
Lobster

What was he using to measure it?

More interesting is the results...

I can't think why a longer length of a ribbon would take significantly longer unless the volume of acid is small and is being effectively diluted by the reaction.

Would there be a proportional effect? If so, it suggests that the figures for 2 and 3cm have become transposed.

I'd be interested to know what the outcome is and the mechanism involved.

Coming back to the original point, I think that calculators have a lot to answer for.

When I did my engineering degree, slide rules were the standard method of calculation with 4 function calculators only just coming on the market. Scientific ones were lab instruments for the most part. Before that at school it had been log tables and one gained an appreciation of rounding and approximating according to the application.

Reply to
Andy Hall

You must be the only one on the planet to operate to a (presumably)

0.1mm tolerance when woodworking.
Reply to
Matt

He is..always likes to be different does MrHall.

Reply to
The3rd Earl Of Derby

Nope. I just have the equipment able to machine wood to 0.2mm reasonably easily. Why would I want to make accuracy less than that when it's no extra effort to achieve a good tolerance? I did also make the point that this was for certain projects and in hardwoods.

Reply to
Andy Hall

Actually, you're wrong in the sense of being the only person on the planet to work to tolerances of better than 0.5mm. I said nothing about 0.1mm, but 0.2mm is perfectly possible for machining, planing and thicknessing operations.

As far as being different is concerned you are right to a point. I am a militant individualist, which means making my own decisions and not following the herd. If the herd coincides, that's fine, and their choice.

Reply to
Andy Hall

But you are not obliged to work in binary fractions of an inch. In the electronics industry, especially for circuit boards, the traditional measurements have been decimal inches, usually working to

3 decimal places (a "thou").

Adding 1.875" to 0.266" and getting 2.141" is no harder than adding

47.625mm to 6.474mm.
Reply to
dcbwhaley

Perfectly true, and I agree with your point in regard to electronics but then for the original example one would have had to convert the eights and 64ths fractions to decimal as well, which is an extra stage.

Generally the dominant scale on the antiquated imperial measures is eighths and fractions of that, which just makes the whole thing unnecessarily difficult.

Having eighth parts to an inch, then 12 inches to a foot, three feet to a yard, 1760 yards to a mile and so on is a nonsense.

Reply to
Andy Hall

======================== It may seem like nonsense but it worked very well for rather a long time and many people still use it in tandem with the new-fangled decimals. It's also worth pointing out that some of the decimal measures ('decimetre' and 'dekametre') are rarely used and almost redundant for most people. Most people who grew up with 'Imperial' have no problems with it and continue to work with it quite happily, despite its claimed disadvantages, and use Metric where it's more convenient.

Cic.

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Reply to
Cicero

Worked? Possibly. Well, I'm not so sure.

Unnecessary extras. For most applications, millimetres or metres and decimal places work well.

I learned all the imperial stuff in primary school and in the past have used it alongside metric.

However, since dumping pretty much all of my imperial measuring equipment and reverting entirely to metric, it's much easier to be certain of measurements - i.e. I typically check twice before cutting rather than 3 times, so it is fast as well.

Reply to
Andy Hall

============================ I think you have a very jaundiced view of the good old Imperial system. It worked extremely well for all practical purposes and it's still fully available for anybody who cares to use it. Look back on the history of engineering, civil engineering, architecture etc. and you have a living testimony to its value. Every cathedral, almost every public building and the vast majority of houses were built using Imperial measurements and they compare very favourably with anything modern.

Cic.

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Reply to
Cicero

Except that it's not. If you go outside the UK into the rest of Europe you won't find it. The only other place where there is significant use is the U.S.

In the UK, by continuing to attempt to espouse two systems of measurement, we effectively end up with the worst scenario -

- compromises on measuring equipment by having two scales.

- most tooling sold in metric

- hand tools sold in different sizes reducing volume of each and increasing prices.

I don't think that their greatness had anything to do with the system of measurement used.

It's responsible for very silly legacies like standard railway gauges which aren't even in round figures in imperial measure.

Reply to
Andy Hall

Surely it's a matter of choice, Andy ... !

Reply to
Frank Erskine

Well I suppose, but factors of 10 make more sense to me.....

Reply to
Andy Hall

And IIRC my handy Electrician's Year Book (1947) has decimals of inch, foot, and yard, in ready-reckoner tables.

Owain

Reply to
Owain

======================== Imperial certainly is available to anybody. Every single measuring implement I own - tapes, rulers, squares - has both scales marked equally prominently. I have at least 6 levels (bought in recent years) and all are measured to a standard multiple of 2', 3' and 6'. None of them is a metric length. Even a recently bought vernier gauge is marked in both Imperial and Metric.

Railway gauges are a different matter again but given their history they wouldn't have been measured in a 'round' metric figure either.

Imperial is very much alive and kicking, and likely to be around for a long time to come.

Cic.

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Reply to
Cicero

I have to mostly agree with Andy, but the imperial system did work very well with bigger units than fractions of an inch. There are many more factors of

12 and 36 than there are of 10, so there were many shortcuts you could take, like 12 x 3", 8 x 4½", 6 x 6" or 4 x 9" all equal 1 yard. To find out how many 9" bricks in a wall 12 yards long you just multiply 12 by 4 and times by the number of courses. It beats dividing 10,973 by 225.

When measuring buildings, especially old ones, I still use imperial measurement sometimes. I can read the printed inches on a tape or 6ft rod much more easily than cm, generally it's much quicker and less error-prone to write down imperial measurements (I use the same convention as the old shillings and pence i.e. 4/11 rather than 4' 11") and more often than not the materials used in old buildings relate to inches much better than mm. Many materials still retain the old imperial sizes even though they're designated in mm, for instance doors, manhole covers, slates and roof tiles. I always use metric on newer buildings, and when I'm levelling or taking readings with the electronic Disto.

Back at the office, if I'm drawing by hand I use a conversion scale rule for the imperial measurements and a normal metric one for the metric measurements. Or in AutoCAD it's dead simple to change from one system to the other because you draw everything at full size. Entering dimensions in feet and inches in CAD is a killer - I sympathise with anyone using CAD in USA or Canada.

We also used a system in the old days called duodecimals, where the basic unit was the foot, and inches were expressed as decimals. 4' 11" would be expressed as 4.9166' feet. With practice you got to remember the decimal values of fractions too. It's still useful today if you want to work in imperial with a calculator.

Peter

Reply to
Peter Taylor

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