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Metric vs Imperial - Practical or Traditional?

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John Olsen06/10/2010 09:29:09
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The Libra refers to weight, a British pound sterling was once a pound of silver. Presumably sterling silver, which is about 97% pure. Good luck with getting a pound weight of silver for a quid now. I do have a lump of pure (chemically deposited) silver here, weighs about 200 grams. Also a half a tin of silver fuse wire that someone painstakingly salvaged from a whole lot of HRC fuses. Ahh well, we are not broke yet.
 
regards
John
Nicholas Farr06/10/2010 11:36:15
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Hi, imagine 10 students sent out for four Pizza's (because thats all they could afford) now for arguments sake all the Pizza's were the same size and flavour and all the students expected an equal share. Dividing up four into ten in metric equals 0.4. Hmmm, 0.4 of a Pizza! not easy to cut with any consistant accuracy, a lot of squabbing ensues. However take an imperial view to the situation and the result to the problem is easy, cut all four Pizza's into 1/3 rds and then cut two of the 1/3 rds into 1/5 ths, each student then gets 1/3 rd and 1/15 th of a Pizza. 1/3 rd plus 1/15 th as a decemal equals 0.3999999999 or as near as you can get to 0.4 of a Pizza. A practical use for imperial mearsurement. QED.
Regards Nick.

Edited By Nicholas Farr on 06/10/2010 11:37:42

Edited By Nicholas Farr on 06/10/2010 11:42:05

David Clark 106/10/2010 11:54:07
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Hi There
What if it is a metric Pizza?
Surely you can have 1/3rd or 1/5th of a metric dimension?
1/3rd and 1/5th are not exclusivley imperial.
regards David
 
Nicholas Farr06/10/2010 12:17:01
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Hi David, maybe so, but fractions were around long before metrication and before the digit 0 I believe. Without the 0 metrication would be dfficult, would it not?.
Regards Nick.
Mike06/10/2010 12:23:23
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Metric and imperial measurements are both man-made, so I (somewhat tongue-in-cheek) propose an entirely new system, based on nature. It would be divisions of the Nautical Mile (one minute of one degree, measured from the centre of the earth). Thus, one standard would suit all disciplines, from engineering to navigation...
Nicholas Farr06/10/2010 12:50:46
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Hi Mike, is not measuring as we percieve it, in itself man-made whatever unit you use? Nature has a habit of producing things in random sizes and shapes of its basic form of things, does it not?
Regards Nick.

Edited By Nicholas Farr on 06/10/2010 12:51:54

Edited By Nicholas Farr on 06/10/2010 12:53:52

Mike06/10/2010 12:54:25
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Hi Nicholas: I suppose you are right, so there goes another fine theory! And I wanted a measurement called the Mike - not out of personal vanity, you understand, but because the smallest increments would only be measurable with a micrometer...
KWIL06/10/2010 13:24:41
3681 forum posts
70 photos
Nick says that nature has a habit of producing things of varying sizes, perhaps its back to nature with cubits and feet?
oilcan06/10/2010 13:51:01
34 forum posts
if students are anything like the ones i come across in Liverpool you'll end up with 4 very stuffed students and 6 hungry ones. but getting back on topic, i'm ambivalent about which is the best system . I hate trying to read 0.5mm graduations on a steel rule as much as I hate the 1/32nds. The one down side of imperial, as far as model engineering goes, is converting fractions from a drawing into decimal places. now for a question, did/does anybody make dial indicators and/or calipers that measured in fractions?
when i built the micrometer scribing block from Tubal Cains 'simple workshop devices'-superb book by the way. very much aimed at the model maker- I used a 32 thread instead of the stated 40 TPI . purely because I could then scribe of in fractions instead of converting to decimal. it did make marking out a bit easier.
Gordon W06/10/2010 15:04:18
2011 forum posts
The metre was originally measured as a distance on the earths surface subtended by some angle or other. We've had all this before deja-vu all over again. Things are the size they are, Whatever they are measured in.
KWIL06/10/2010 15:31:07
3681 forum posts
70 photos
Yes www.theToolwarehouse.net in USA does a caliper with, imperial, metric AND Fractions!
Dinosaur Engineer06/10/2010 16:05:42
147 forum posts
4 photos
I don't understand why some people find it difficult to work with both systems . Today we have computers and calculators that will instantly convert from one system to the other to the umpteenth decimal point. I remember having to use 7 figure log tables in the toolroom to work out some conversions and trig calcs. We even had a 500 inch rotary slide rule ( Fowlers ?) in the jig & tool D.O. for the non-critical sizes/dims/calcs.
Today it's so easy !
 It's just as easy to turn something accurately to 1.000 inch or to 25.4mm or conversely to 0.984 " or to 25mm if you have the correct measuring gear.
The main problem I see is the reducing availabilty of imperial stocks of materials. 
As more designs are done in CAD , then it becomes much easier to see the effects of changing material sizes, from one system to the other, to the overall design and work out the compensating changes required. To this end it would help if designers published clear layout / assembly drgs. ( ideally in CAD) to save having to wade through lots of detail part drgs.
chris stephens06/10/2010 16:10:38
1049 forum posts
1 photos
Hi Oilcan,.
Yes, they do make them, I have two different ones. No let me correct that, I HAD two, one a Swiss made dial caliper, now sadly broken. The other a digital one, I think from Warco, has been "borrowed" by the workshop Gremlins, it was there one minute and gone the next. This is a shame because it was my favourite caliper, it had auto ON as well as auto OFF. Must buy another one at the Midlands, if for no other reason than to encourage the pesky little blighters to return the first one. Has anybody else found that this tactic works on them? 
 
On the other issue, I agree the ONLY problem (for our usage), apart from prejudice, with Imp is the use of fractions instead of decimals. A Thou is a much more friendly unit to work to than a 0.01mm. Who really wants to work to two and a half of any units, (the Metric equivalent.)?
 chriStephens
 
 

Raymond Anderson06/10/2010 17:01:38
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785 forum posts
152 photos
attn niloch,
                        Being a bricklayer to trade I feel I can jump in here re brick and block sizes,
All standard bricks and blocks are in metric sizes  you can still get imperial sized bricks but they are regarded as specials  if you ever have to match in metric blocks into an existing imperial block wall you can look forward to having mortar beds that you could sleep in.
                                                          Regards 
Ian Abbott06/10/2010 17:37:54
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279 forum posts
21 photos
For a lot of jobs, I use the spray paint method.  Hold the pattern up against the material, a quick spray over with mat black paint, when dry, cut around the line with a big saw / chisel / hot axe, job done.
 
And when I wor a boy, it wor uphill both ways, barefoot, three feet o' snow, in the dark. 
 
Ian 
ady06/10/2010 21:52:18
612 forum posts
50 photos
I prefer the Mayan base 19 system.
 
It's far more accurate for those big jobs.
John Olsen06/10/2010 22:02:33
1294 forum posts
108 photos
1 articles
Actually we should toss all the measurements and change the way we count to base 12 instead of base 10.
 
As well as the modern digital calipers that do fractions there were  Vernier calipers that had them as well. I have an 6" Mitutoyo one, must be nearing its 40th birthday by now. It has Inches by thous on one side, and inches by fractions on the other. The calibrations are in sixteenths. The Vernier for that side has 8 divisions over 7 sixteenths of an inch, so it reads down to 1/128". Not that the fractional side has ever proved to be very useful.
 
One thing that I hate about the older designs is having to add up all those strings of fractions with different denominators.
 
The difficulty with attempting to standardise is that the old standards never really go away.  So you end up having to deal with all of them. There are after all still people using Holtzapfel screw threads. The supposedly metric European countries use what look at first sight like some very unusual dimensions for plumbing threads, but they actually translate to British standard pipe. I started out with a metric Unimat 3, so bought metric drills and metric taps and dies, including some of the fine series ones which are actually quite nice...8mm by 0.75 for instance. But now my workshop is full of a mixture of metric and Imperial stuff, often on the same job. On my launch engine all the bought screws and nuts are metric, but anything screwcut like the glands and ends for the rods is Imperial. The material used is a mixture, sometimes you can buy inch  stock and sometimes you can buy 25mm. Oh well, at least it runs well. Good luck to anyone trying to fix it in 25 years time!
 
(The metric screw pitches are badly chosen from the point of view of screwcutting, an Imperial gearbox is much simpler than a metric one.)
 
regards
John
oilcan07/10/2010 00:10:11
34 forum posts
Thanks Kwil and Chris for the heads up re fractional calipers. Now i know what to look out for at the ME exhibition.
and Ian, just three feet of snow!!! shear luxury !!! 
Sam Stones07/10/2010 02:24:38
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922 forum posts
332 photos
These days Nicholas, I prefer my Pizzas cut into four quarters. Six pieces is more than I can eat.
 
Or should I go for two pie radians?
 
In my tool box, I have a 1 to 2 micrometer which I hardly ever use. It came with my 2nd hand ML7.
 
On one side of the line it's graduated in decimals, while on the other side it's in eighths (I'm talking inches of course).
 
I mis-read it on an important job (only once) and, as a result, lost quite a valuable customer.
 
A lesson well learned!? 
 
Sam

Edited By Sam Stones on 07/10/2010 02:25:56

Ian Abbott07/10/2010 19:22:10
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279 forum posts
21 photos
Speaking of pizzas, which originally came from China, shouldn't the dividing of such be undertaken using Chinese measurements.
 
The expert sitting across from me says that for linear measurements we'd be using 毫 (hao), 厘 (li), 分 (fen), 寸 (cun), 尺 (chi) and so on, which of course would only work for dividing around the circumference.  尺 being about one imperial foot.  To divide into segments 度 (du) would be the same as our degree.
 
That's about as much Chinese translation as I can manage for one day.
 
Ian 
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