I had my left leg casted when I was in kindergarten. When it was time for the cast to come off, the doctor used a power saw. I was worried that it would cut me, but the doctor put the blade against his skin, and turned it on — it buzzed, but did not cut him! He put it against my hand — nothing! Then he put it against the cast — and it cut through in a whiz!
Years later, I figured out that the blade was vibrating. Flexible flesh would simply be wiggled back and forth, but rigid casting plaster would be cut. (Doctors know this little gem as the Stryker saw, and also use it to cut bone without cutting surrounding soft tissue.)
Yesterday I saw the same thing on TV, adapted for the home shop: The Fein Multimaster. [Caution: A loud TV ad automatically begins playing. It's in a tiny window, upper left hand corner. Click to get the controls.] The great thing about the Multimaster is the triangular blades, which, since they don’t rotate or reciprocate, can go into tight spots.
What? Oh, of course Toolmonger’s discussed it. The key to loving it, though, is to see it as a saw, not a detail sander, which is apparently how many folks were introduced to it.
I want one. Great little tool.
Urgh, but $300 plus? Urgh,