Hello Duncan
"I agree that they loosen up on repeated fitment"
Once you do what I refer to as burnishing, the hole size remains much more
stable. I suspect that not only does it smooth the inperfections of the
wall, but expands the metal just a bit where it becomes less resiliant to
change.
I talked to a guy who used to refirbish critical gear components of Gruman
carrier aircraft. Before final reaming, he would use a hydraulic expander
to first enlarge and stabalize hole.
Making a dogbone or first hole slight larger than the second goes even
further to preventing damaging fit.
Ron Parigoris
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