[Shop-talk] Micrometers

[Randall]

> A mechanical
> vernier caliper may not have any way to set the zero datum 
> but all of my
> digital ones do. 

Well, so do my dial calipers.  Still, it would be a major PITA (and
potential source of error) to have to re-zero and then reset to the first
measurement in order to transfer an outside to inside measurement (or vice
versa).

Out of curiosity, I picked up a 2" gauge block & micrometer and checked one
of my under-$20 dial calipers against them.  The external measurement of the
gauge block was right-on, while the internal measurement of the micrometer
set to 2.0000" (and checked against the gauge block) read about 1 needle
width high, much less than the .001" resolution of the calipers.  Probably
with a lighter touch, it would have been dead nuts as well.

Randall