Wild_Bill wrote:
(snip)

Most times around the shop, parts don't need to be perfectly clean, but
optics elements do.

At one time, I was machining some IBM bearing housings on a Hardinge
SuperSlant. The bore had a +/- .0004" size tolerance, and the same
tolerance for concentricity with the bore on the other side, machined
in a previous op on a different machine. Holding size was no problem,
but when we started, we were rejecting 30% for concentricity. We were
cleaning the parts before inspection with standard pink shop cloths.
One night I tried white paper towels instead. One out of 40 parts
failed. Cleaned some of the older failed parts with paper towels,
they now passed.

David