Hit 3 of mine with a 40 micron belt for two passes per side then slowly stropped em by hand, hair popping shaving sharp. Sold to some new Bussekin addicts for my cost.
Secret of SR101 or INFI, raise the smallest burr you can feel then slow strop em, they will shave.

Out of the carboard they would pushcut paper but just. Now I can slowly zig-zag paper or shave hair.