Sharpened every head I"ve used on paper wheels on a grinder, even the insert blades. You have to be really careful.
I do so if they don't pass muster or if I've shot them through a deer and ready to shoot another deer.
Hit anything with a file if I need to change angles, and then hit on the paper wheels.
If you use wheels, make sure to turn the grinder backwards so the wheels spin away from you and sharpen on top so if the wheels grab the blade, it throws it away from you and not through you....
