I bought a rotary cutter & it has sharpened my old blades real good . the problem is that if your blade is not dull yes dull it will ruin your blades it has to be dull that can no longer cut. Also when it says 20 times when you go up & down that is once. not twice . you have to do 20 x then turn the sharpener all the way around & do it 20 more times . then 10x then 5 x remember to turn the sharpener all the way around afer each set. when you do that your blade will be sharp. just run the blade back & forth slowly. Saves a lot on your blades. shrabar.