I did a post on this subject before and received very good information. I plan to use an angle grinder to sharpen my blades. However, my father is driving me crazy because my blades are in pretty good shape and he says that I need to use a hand file to sharpen them so that I will not take to much metal off of the blade. What do you think about this issue. I want to keep my customers happy and avoid any potential problems. I plan on sharpening blades every 10 to 20 yards.