By no means am I one of the experts but I have chamfered my Norton 4/8 successfully. From what I have gathered the goal is to take off the sharp edge and not much more than that. All I did was very lightly round off the edges with my flattening stone. I did not have any chipping or uneven chamfering. I think the key to this is "lightly".
I hope this helps and good luck,
Marc