Originally Posted by
Peter Evans
Peter, a thought (I have not done this).
I find that old blunt files and rasps after citric acid sharpening tend to be less aggressive than they would have been when new, still cut well, but smoother. Very blunt rasps usually still have a shiny flat after sharpening, but cut ok. The teeth do not last as long as new I suspect. Note I am using the files mainly on wood.
If you were to deliberately blunt a rasp, and then acid sharpen - maybe you will get a smoother but still effective rasp.
another Peter in brisk Sydney winter