I was looking for a way to make planer knives sharper. I bought several sets of 12 1/2" blades that have become dull so have I tried this sharpener to see how it works. I know it says there is a holder for 6" blades but as I was hoping it worked fine with 12 1/2" blades. After sharpening of a set I can say the tree passes my planer with less effort.Since then I've sharpened 2 more sets so 6 are ready when I need them.Wish I'd bought this many years ago