</font><font color="blue" class="small">( They really don't seem bent, just dull. The only real thing I see is that the blades didn't rotate freely on the stump jumper. I can see how this might cause it to vibrate but I'm just guessing.)</font>
It is my understanding that the blades on a rotary cutter should not really be sharp. I read somewhere that the leading edge should be 1/16" thick since a rotary cutter "shreds" rather than cuts.
On my old cutter I used to get strands of grass caught between the blades and the stump jumper and it would start vibrating. The blade(s) would then be "stuck", not swing freely.
Easiest way I found to clear them was to take a hose nozzle and blast them with water while jiggling the end of the blade up and down a little so the water could blast the trash out. That cleared it up every time. Of course be sure to shut the tractor down completely before sticking your hands up inder the cutter!
I tried WD40 on them but that didn't seem to help. If anything it just made the dirt stick to them worse.
Bill Tolle