Sharpened the blades on a couple of four blade discs, using speedie's angle grinder method. As vint_mow mentioned, be careful of heating the metal, which I came close to doing by lingering too long on some passes. A few lift passes does the trick, and I didn't aim to make them like razors. Just to give them an edge over factory shape.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!
