I can't tighten my blade onto the shaft enough to keep the shaft from spinning in the blade. This problem has gotten worse over time, so finally I can't use the saw anymore.

If there was some way I could lock or jam the armature or the shaft to tighten and then later, loosen the bolt on the end of the shaft that holds the blade I think I would be OK. I have never had this problem before, but now I'm stumped.