: I've a small collection of files that are dull from use, mostly
: sharpening machettes. Seems a waste to throw them out. Can they
: be used for anything other than steel scrap?

: John

You can sharpen them, I believe. Although I haven't tried it myself I read years ago in an ancient DIY book that files can be sharpened using muriatic or phosphoric acid. Muriatic acid is readily available, stores selling swimming pool supplies carry it; it's hydrochloric acid actually.

I suggest you degrease them first with TSP then put them in a nylon net so you can lift and agitate them without skin contact, and immerse them in the acid. Check every half-hour or so; once they lose that shiny look they are done. It should probably be done outside and of course the files should be rinsed thoroughly and maybe sprayed with WD40 to keep them from rusting. This a very old trick.