Rusty Burrs

Mark said,

We redistributed the good ones and sent the dull ones to Gesswein for
recutting.

I’ve never tried it on burrs, but a technique used by machinists and
others to ‘sharpen’ dull files, is to submerge them in nitric acid for a
time. The acid eats away the metal, leaving a sharp edge. Of course you
have to take pot luck on the evenness of the cut after the acid etch. The
new edges don’t last as long as a new file, but what the heck, you couldn’t
use it the way it was. Usually the files have to be relegated to a
‘roughing’ job.

Dave