Sandpaper works, but you' ve got to make sure you' ve got it snugged down on a good, flat surface or it' ll round off the edge instead of making a flat ' V' edge. You' ll wind up with a ' U' instead.

I use a file to establish the edge, then a diamond hone to work off the burr and then a good stropping on leather impregnated with jeweler' s rouge and glued down on a block of wood to polish it off. It gets my broadheads so sharp you can' t even look at ' em without safety glasses.