I was using a rat-tail rasp this morning and noted my comment on it that it had been sharpened. Did you know that you can have sharpened files, rasps, and other such tools?.
I have used Boggs Tool https://boggstool.com/. They cost just a few dollars each. Since you have to pay shipping, it pays to send a few at once, or get together with a buddy. If the tool is beyond sharpening, they will discard or return at your request. They told me they'd make my Nicholson patternmaker's rasp sharper than new.