A lot of us have purchased rotary blades from Harbor Freight. They're meant for carpet cutting but fit the major rotary cutters. I've been happy with mine, but some people have had problems. (Harbor Freight reportedly will replace or refund if you're not happy.) If money is tight, you might try their blades - much, MUCH cheaper than anywhere else. I have heard more bad reports than good ones on rotary cutter sharpeners. Usually when my blades go bad it's because I ran over something I shouldn't have and caused a nick in the blade. Sharpeners don't help with that.