I'm not sure where Phil Sharpe came up with ones needing two orders of magnitude more precision in the measuring equipment versus the tolerance to be held. I was taught in both Chem classes, and as a machinist, that a single order of magnitude was going to be "good enough". Thus a balance that is accurate to .01 grain is appropriate to accurately measure differences of .1 grain. And a micrometer that accurately measures to .0001" is needed to be sure you are holding tolerances of .001". And of course neither a brand new digital micrometer nor a lab balance, is worth a hoot until it is calibrated, by equipment that itself is calibrated... onward up the chain until you hit the bureau of standards (NIST?)
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<br>Regards,
<br>Scott
