R. I. Nelson wrote:

>>> but we still tried and usually achieved 0 tolerance.

>> Saying stuff like this that obviously can't be true just eliminates your
>> credibility.  

> This one gives readings of  0.0001 [...] There are micrometers available 
> that have a resolution of 0.00002" and accuracy of 0.000015"

What Olin was responding to is you saying that you achieved "0 tolerance".
When you measure that you're "right on" with an instrument that has 500 nm
tolerance, then you only know that you are within +-500 nm of the target.
(Simplified a bit.) You can turn and shake that as you like; that's a
tolerance of +-500 nm, and not a tolerance of 0. You won't find an
instrument with 0 tolerance, so you can't know whether you achieved 0
tolerance. You only ever will know what tolerance you have achieved within
the tolerance of the instrument you use to measure.

Gerhard

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