toni,
sharpening the inside of a radiused cutter is a bugger no matter the type of steel. one of the tricks i use is to shape an india stone on a concrete sidewalk to a radius somewhat tighter than the cutter, then it`s a matter of free-handing the stone and cutter `till you have an even burr. once you`ve raised the burr i use a buffing wheel charged with jewelers rouge on the inside surface and a leather covered " power-strop" on the outside. once the edge is established it`s only a matter of touching it up on the wheels with rouge to freshen the edge.