Unless one is a machinist, it may not be cost-effective to regrind BB, nevermind the case-hardening. What does one have to lose by grinding/polishing BB with carborundum-laced grease?...BB is already toast! Install a sealed BB until an original replacement turns-up...riding is paramount.
On copper-plated bikes/parts, is it preferable to keep polished or should one leave oxidation/patina a la Antiques Roadshow? Seems that if tubes aren't properly polished, the copper-plate may not look satisfactory...similar to chrome-plate. Then there's clear-coat over copper...where does it end...perhaps better left as-is.
Jack Romans
Sacramento, California