I use a 3m 36 grit 7 inch fibre disc on an angle grinder.
3M rocks!
These remove metal fast and last longer than the others. They don't generate the heat that a grinding wheel does. Plus, it puts a beautiful edge on the blade. Customers love it. I've had guys look at blades ready for others to pick up and exclaim "you did this?" as if they were running home to bring theirs back. Makes me feel good. Oh yes...they make short order of a bush hog blade, too.
They have some new discs out that are suppose to remove metal even faster and last longer. I'm going to try them Nexxt.
My nexxt purchase
Philip...let me know if you have a 7" angle grinder. I can send you one.