Knotter knives. OK to sharpen? Or replace?

As the topic title says. Is it OK to resharpen knotter knives? 

 

I have a 1990 John Deere small square baler that I've just got back into working order, but the cut twine ends are very ragged, which seems to indicate the knives are past their best. As I live on a small island with no access to a dealer, it would mean ordering knives online and hoping the seller is willing to post to me. I'm a time-served carpenter, so sharpening blades is not a black art to me, but would it alter the tolerances of the knotters if I did this? 

Knotter knives. OK to sharpen? Or replace?