|I have been using rotary cutting for a couple of years, and purchased the sharpening kits for the 45mm & 60mm to prolong use of the rotary blades. This was more environmentally friendly & to save money. I have sharpened both the 45mm & 60mm blades. After cutting lots of fleece, my hand /wrist starting having shooting pain. After placing in new blades and the fleece cutting like butter, I realized the problem was the blades I sharpened are not anywhere as sharp as a new one. I have not been able to sharpen the used blade to be the same sharpness with these blade sharpeners as as a new one. So long story short to prevent hand/wrist problems just replace your blades with a new one. Saves on pain, and speeds up your rotary cutting.