I just found out JO bloks increase in size over time naturally?????
Also they expand .0000115 * Length for every 1.8 dgrees F above 68 degrees.
They are calibrated with grren light due to its short wavelength.
If only i could find out what wringing means, how its done.

Any who are interested check out
http://ts.nist.gov/ts/htdocs/230/233...pubs/MN180.pdf
for THE nist gage block manual