What he said-and if they're dull, the edge is bound to have a gouge or two in it in which case there's nothing to do but buy new. I bought a cheap pair of Craftsman side nippers to keep with my guitar stuff for trimming strings.The jaws swing in an arc and it's quite hard put a new edge on each jaw and have the jaws still meet uniformly along the edges.
Gotta tell ya Dave, I live here and I've never heard of "Sir" cutters. I think it was a typo.