Like anything else their are opinions but 57 to 62 comes to mind without looking it up and that all depends on the steel. To low and it won't hold an edge. Too high and you'll never get an edge. I always wonder about using Damascus (as it is used in knives) because which metal are you honing and which was picked for the heat treat method. The "n" in 15n20 is nickel. Great for pins :<0)

And thanks Pringr but some one of vast steel knowledge could answer this much better than I. Remember I said " wild guess"