- File burrs from rounded head.
- File facets onto round shafts.
- File heads to the next size down.
- Buy a variety of sizes for easy access.
- Buy in varying coarseness.
If you accidentally smear off the shoulders of a nut or bolt head you can get a second bite at the cherry by grinding that material away. Using standard spanners you go down to the next size (in combined metric/imperial sets this may not be as bad as it sounds). If you own “wall-drive”/] spanners you may not need to do any filing but a minor cleanup won’t do any harm.