I just buy new blades. I try to get them on sale. I purchased a rotary sharpener that Nancy zieman advertised on her show. I sent it back after using it and they gave me my money back. If it isn't going to work the first time I use it, it goes back. I have a tendency to throw things in the trash if they don't work. Dh said to just purchase more blades. I buy the blades from the same manufacturer as the rotary cutter. That way they can't say that is the reason for the dullness. I would send the sharpener back and tell them it reversed itself and dulled your blade because it won't cut thread.