That's right, the already made objects don't change -- but, at least in
theory, when you change the definition of your units, all the *rulers*
do. So your old set of gage blocks, of which the largest is
1.00000+-.000001, suddenly became 1.00400 or some such, because you'd
redefined the inch to be significantly smaller than it had previously
been. This was a real problem even with the amount of definition change
in the 1959 standards issue (a change that was out in the third decimal
digit of a millimeter, roughly 100 microinches per inch). Fortunately,
there weren't that many objects made a couple feet long to a tolerance
under a thou that needed to be calibrated (though you could easily read
the difference with "old" and "new" six-inch micrometers, if they were
top grade instruments).
Shannon DeWolfe wrote:
> Donald,
>
> I do not agree. If an object was made before the redefinition of the
> inch, the thing itself did not change with the redefinition. If the
> decision had been taken to make an inch equal to 25.0 mm, rather than
> 25.4 mm, the object would still be the same length.
>
> The only thing to be aware of is whether a dimensioned drawing was done
> before or after the redefinition. That is true whether the difference
> between the "old" inch and the "new" inch is a micron or a mile.
>
> Regards,
>
> Mr. Shannon DeWolfe
> --I've taken to using Mr. because my name misleads folks on the WWW. I am a 54 year old fat man.
>
>
> On 1/14/2011 3:26 PM, Donald Qualls wrote:
>> Too much existing work already in the old inches to change the inch by a
>> significant amount.
>
>
> ------------------------------------
>
>
>
>
>
--
If, through hard work and perseverance, you finally get what you want,
it's probably a sign you weren't dreaming big enough.
Donald Qualls, aka The Silent Observer http://silent1.home.netcom.com
Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.
http://groups.yahoo.com/group/gingery_machines/app/peoplemap/view/map
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