I use a 3" cut off wheel in my Shearline mill. I shape he cut off wheel first to cut the proper shape for the nail nick. This is a very fast way to do it and you can do it after the blade is hardend so you have a nice clean nail nick.
I don't know the name brand but I get them at Home Depot or MSC they are 3" in diameter, 1/4" hole, 35thousanths thick. I shape it with a stone designed for that purpose.