I used to take my chipper blades to a machine shop, until they decided to try a different angle on the blades and ruined 4 sets. I do mean 4 sets, not 4 blades. The blades were sharp, but would not cut. To say I was p-ss'd is the understatement of the year. I sharpen them myself now on a bench sander using 50 grit belts. You need to use a good quality bench sander with enough power so the belt won't slow down when you put a little pressure on the belt. The blades look like they were machined when finished and cut just fine to me.