I've asked the same question, here, several years ago, and after some encouraging remarks, I tried it. It works, though not as well as a dedicated one, because the metal in the firesteel is rather soft. Also, some of the firesteel's metal can rub off, leaving dark marks on the knife blade, and an uneven surface on the firesteel. However, these are minor issues, and a firesteel is definitely better than nothing. If you are carrying more than one knife, then using one knife to steel the other knife will work better than using a firesteel.