On Monday, January 13, 2020 at 12:35:46 PM UTC-5, Clare wrote:

Why is everyone missing the obvious - USE A FILE!!!!! Rub it on mild
steel, or a casting, and make PURE iron filings, not mixed with
carborundum or other abrasives or other chemical compounds.

pyotr had that three days ago, but it's just too obvious for rcm. First, you have to dig an iron mine. then you have to smelt. then you have to make steel for the file. then you have to make the file. then you have to harden it. THEN you can start filing the iron.

Far easier to just buy a box of Wheaties.