It is primarily an issue of what state the steel is in. Annealed steel is easy. Even super high alloy stuff like 3V is not that bad. Hardened steel, even "spring tempered" stuff, not so easy. I do some light filing on some steels that have a fair bit of alloying elements and they are not bad at all as long as they are annealed. With that said, John White did the bevels on a little wasp waisted dagger of hardened W2 a while back totally with files.........he just trashed 3 big files in the process.