Every so often I box up a load of files and send them off for sharpening to
Boggs Tool Co.
All I have to do is give them a note with a count of the number of files in the package. They sharpen them all and send them back with a modest bill.
After they use their 120-year-old steam/'abrasive blast process to sharpen the files they give them a quick test. Those that don't pass the test get red paint on the end, and come back at NO charge. Even those that don't pass are far sharper than they were before.
They will do ANY kind or size of file - nut, fret round, rasp - whatever.