Thread: Imperial vs Metric system

They are a nice thing to have in shed if you use a lathe.
If you want 3 cm diameter you just measure around the outside and it tells you the diameter.
You can get a lot closer using them because any deviation is enlarge by pi.
is very easy to see the difference between 3 and 3.05 cm.

Used to use them in a rubber factory when we had to grind rubber rollers down to 8 inch by 12 feet long (printing industry).
And you needed to be accurate.

Is there going to be a run on diameter tapes now??

Originally Posted by Bedford

Attachment 294469

Are they 32mm inches? As per 'system 32'? (Which I'd never heard of before now.)

Originally Posted by Bedford

The white one has ten eighths!

Which would make them tenths, no? As in decimals?

Originally Posted by bob ward

Ye olde length gauges at Greenwich Observatory

Bob
I took exactly the same photo when I visited Greenwich England, in May this year.
Just stood & stared at it for a while, thinking about how these measurements came about & how they have been used over time !
regards
Bruce

Originally Posted by Bryan

Which would make them tenths, no? As in decimals?

Electronic components are all inches in 10'ths. For example Integrated Circuit pin spacings are 0.1" and standard DIP packages are 0.3" wide pin to pin

Although surface mount component pitches are tending more to metric these days..

I wonder if that tapemeasure is a special for electronics use? On edit... no

Regards
Ray

Attachment 294469

The Shang dynasty was 1600 to 1046 BC (yes BC=Before Christ). They had a unit of length called the "chi". 6 chi was one "bu". One Bu equals in modern si units 1.0050 meter. Do you think it is a coincidence, or could it be that Mr. N. Buonaparte had based his meter on one Chinese bu? Now, 300 bu was one "li" or in modern si units 301.5m.

No, I am not trying to say the above tape measure dates from the Shang dynasty. But the Chinese had measurement systems a very long time before any inches or meters were invented in the "western world". I highly recommend to read this Wiki page. It may go some way changing how we like to look down onto anything coming from China.

Chinese units of measurement - Wikipedia, the free encyclopedia


Also of interest in the context of above tape measure:

Japanese units of measurement - Wikipedia, the free encyclopedia

Here we go. Solved the mystery of the white tape.

1m = 30 Chinese cun

You can verify this for yourself, by using this Chinese measurement calculator:
Chinese Measurement Converter

enter 1m and choose the cun as the output "currency of length"

The white tape measure with cun at the top and cm at the bottom was supposed to be sold in China, not in Australia. I think this is a wonderful example to show the advantages of everybody converting to the metric system. There is not only a competition between the metric system and the english-imperial system, there are many dozens of other incompatible sysems that are unified with the one metric system.

Thanks Chris... that tape measure makes sense now.

100 mm = 3.00 cun

Regards
Ray

Originally Posted by RayG

Thanks Chris... that tape measure makes sense now.

100 mm = 3.00 cun

Regards
Ray

Ray, now imagine the Brits would have adopted the cun as their inch, instead of poisoning the Chinese with Opium. Today our Chinese lathes would have cun leadscrews. A pitch of 0.1 cun would equal exactly 3.0000mm. No need for those silly 127T gears. We could cut threads in either cun or mm pitch using the same gear sets. Cun taps and dies would be interchangeable with metric taps and dies. A can of beer would be exactly 10 cubic cuns or 270ml..... or would that be 12 cubic cuns = 324ml.... anyway the world would be different.

• 

What about the Hybrid System? I remember when we changed to Metric. Tapes had Imperial on one edge and Metric on the other. Some of the older blokes wanted to change over slowly.
They'd measure down the Imperial side to the nearest (under) inch, then go across and count up then add the mills to get measurements like '4 foot 6 and 15 mill'. Worked, too.

The Hybrid System didn't work too well for NASA though, with the Mars Climate Orbiter. Mars Climate Orbiter - Wikipedia, the free encyclopedia

I work in both Imperial and Metric units all the time, with my calculators. Just in the extra time it takes to do calculations in Imperial, I reckon it must cost the US heaps.
It often takes longer just to convert a calculator from Metric to Imperial, than to create the Metric version in the first place.

And if you want to print out some Diameter Tapes (PI Tapes) to see how they work, try this: Printable Diameter Tape Templates. Wrap around Pipe to Measure Diameter

:

An old boss of mine used to complain that metric units were unnatural. I said it was just familiarity, and if he could get used to calling an inch twenty five millimetres it would come to mean the same thing. But over the years I've somewhat come around to his view.

I think a good scale is one that is easy to express. When describing a lathe chuck, inches are convenient because they give a small whole number that's easy to relate to. A six inch chuck sounds a nicer thing that a hundred and fifty millimetre one. I suppose you could call it a fifteen centimetre chuck. But that would make you a girl, right?

In the sub-inch range, millimetres work better. A ten mill bolt is just simpler than a three eight one. But what happens when you get below a millimetre? Would you rather say - even in your head - point two five mills or ten thou? Point oh five mills or two thou? Point oh one six or six tenths? You could legitimately call that sixteen microns, but in the real world you might feel like a stupid poser or something. I think I would (unless my name was Gardiner or Fehring). The point is that although thousandths and ten-thousandths are tiny divisions of an inch, they can be expressed as whole, simple numbers, and that's attractive; reassuring even.

I guess no one system is going to be in its comfort zone at every possible scale.

Here's the tapes, both 5m/16Ft, both bought at the same time from the same shop.

Thanks to all that came up with the info, and I think the clue to it all is in the third pic.

P1050342.JPG


P1050348.JPG

P1050347.JPG

I recall a story from years ago and I have no idea of its source that when there was a push to get the US to go metric it was industry based. All the major US auto manufacturers told the govt that if the country did not convert then they were going to anyway come what may. Subsequently that is what happened. It was less than interesting working on cars during the time of conversion here in Oz as you never knew what spanner you were going to need when a new model came out as some of the car was metric and some imperial. All my imperial tools have now got rust on them and my son a mechanic has never worked on an imperial car. I offered him all my imperial tools and he told me to throw them in the bin and he is not far wrong.

It was less than interesting working on cars during the time of conversion here in Oz as you never knew what spanner you were going to need when a new model came out as some of the car was metric and some imperial.

My last car, a 1993 Falcon had a mix of both metric and imperial. I have not done enough work on the current one (2002) to tell how much has changed.

Dean

Originally Posted by Bryan

In the sub-inch range, millimetres work better. A ten mill bolt is just simpler than a three eight one. But what happens when you get below a millimetre? Would you rather say - even in your head - point two five mills or ten thou? Point oh five mills or two thou? Point oh one six or six tenths?

This only appears so, because you obviously grew up with the imperial system. To you, "ten thou" or "five mills" have a meaning that you can relate to. You have a feeling for how much ten thou is. You instinctively know how much slop you will feel if a shaft is "five thou" smaller than the bearing.

I grew up metric. I have a good feeling how many 1/10's of millimeter I will remove with one file stroke. I know in advance how the slop will feel from a shaft being one micrometer smaller than the bushing. But "five thou" have absolutely no meaning to me. Only after I translate your "five thou" into 0.127mm it gets a dimension: aha, he means a little more than one tenth of a millimeter.

What I want to say is, it is not one system being superior to the other. It is not one system lending itself better to visualization than the other. It simply is that your brain still thinks in, and compares everything with the system that you once grew up with.