Re: [CAD_CAM_EDM_DRO] Slightly off-topic : History behind lettered drills

Hi,

I don't really know why there is always so much fuss over whether you should
be metric or imperial - both, or should I say all, measurement systems have
their particular benefits and drawbacks and ought to be able to co-exist
amicably. The biggest benefit with the imperial and other duodecimal
measures is that they tend to be easily recognised and visualised sizes -
the size of your foot, the length of the last joint of your thumb, an
armspan etc., however, when you get to thous', visualising them becomes
difficult. The metric system, on the other hand, is very difficult to
visualise and, infact, is also difficult to teach as children cannot easily
work with the two most common measures, the metre and the millimetre so,
over here at least, schools start teaching using the centimetre - a
measurement that the kids never use again once they leave school. I suspect
that the choice of measurement system for a country is largely political
rather than practical and has a lot to do with who the politicians wish to
show allegiance with. After all, there are still hundreds of different
measurement systems in use throughout the world, not just imperial and
metric!

For my own part, I use whichever measurement system happens to fit the job
best and tend to work in millimetres for sizes up to a foot and feet and
inches above this. The silly thing is, of course, that if I go to the lumber
yard I find timber in stock sizes of 1.8 metres x 3" x 2" and 2.4 metres of
2" x 1" etc. Almost all building materials are still in imperial sizes which
have been converted to metric giving silly numbers (no one, of course, has
changed any machinery to actual metric sizes and it would be silly to do so
as repairs to existing buildings would be difficult to match). However, our
government seem set on continuing the 'metrication' of the country and, at a
hardware store where I occasionally help out with holiday cover, we now have
to sell the nails which were previously 1UKP per 1lb at 1UKP per 0.457kg -
as far as we're concerned they're still 'a pahnd a pahnd' but now with a
slightly French accent!!! ;o0

One other thought - any doudecimal measurement system (based on units of
twelve) is more flexible as 12 has more factors than ten - so you can have
1/2, 1/3, 1/4, 1/6, 1/8, 1/12 etc. where in the decimal system you get 1/2,
1/5 and 1/10 and that's it. It was a sad day when we stopped having 12
pennies to the shilling! Wasn't there some confusion between metric and
imperial units on a spacecraft somewhere?

Ian
--
Ian W. Wright
Sheffield UK

----- Original Message -----
From: "dave engvall" <dengvall@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
>
> Mixed measurement systems are a problem.
> IMHO if we had put Km on our interstate hwy system and sold gasoline in
liters we would be metric now.
> Most of the international manufacturing concerns (car companies) have gone
metric. Too many inch tools are coming out of Boeing to
> convince me they do much in metric except the military stuff.
> Getting standards in the early 19th century when the US started to convert
to interchangable parts must have been interesting.
> <ugh>
>