From: Timothy Partridge (timpart@perdix.demon.co.uk)
Date: Tue Aug 19 2003 - 15:34:01 EDT
John Cowan recently said:
> Marco Cimarosti scripsit:
>
> > You could generalize it a bit: Alignment Of Metric And Imperial Units Whose
> > Difference Is So Small As To Be Pointless.
> >
> > E.g., I never understood why on earth metres and yards should be kept
> > different. In a public park somewhere in UK or Ireland I have seen the
> > following sign:
>
> Because the yard isn't just an isolated unit, like the pound in various
> European countries. It's part of a coherent (if profoundly messy) system.
> If we reduce the yard by 9%, the inch has to shrink too, and the last
> thing we want is to try to fit a 1/4 inch bolt (6.35 mm) into a nut
> whose inside diameter is only 5.81 mm. It's bad enough to have to have
> two kinds of hardware already: having incompatible things both labeled
> "1/4 inch" would be the facilis descensus Averno indeed.
In the UK the inch is now defined as 25.4mm rather than a subdivision of a
standard yard kept under lock and key. If you peruse electronics catalogues
you will discover that many components have leads spaced at a pitch of
2.54mm which seems a remarkable degree of accuracy. When I was younger they
were a nice round 0.1".
Tim
-- Tim Partridge. Any opinions expressed are mine only and not those of my employer
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