I done it! Have 2 700 series corded Norelco triple heads. Unwilling to
fork over 25+ bux for new heads, I cleaned them, and then sharpened
the blades by rotating them in reverse direction with medium pressure
against some wetted 4000 grit paper on a flat surface. Worked like a
charm. They cut like brand new.

Still easier to grow a beard. I haven't shaved for 29 years now. How many
others go my route?

Karl