I have a dumb rotary blade story too. I changed the blade, put it back together right...but....I tightened it way too much and the blade wouldn't turn. I know, you would think I would have easily figured that out. No not me, I changed several blades, thinking I had a bad package of blades!!! I even bought a new cutting mat (that was needed anyway) thinking it was ruining my blades. Soooo...don't tighten your screw too tight, that is my dumb experience!