I own a rotozip tool. I have used it mostly on dry wall and some on plaster and tile. It works well for its designed applications. I have also used it on fiberglass. I find that on tougher materials that the saber saw or sawzall is better. The problem with the rotozip is that the bearings are not designed for heavy side loading, and that the cooling is marginal. I have had to disassemble mine several times to clean out the interior, the cooling blades began hitting the housing and I had to make slight modifications. For really heavy grinding I find an air driven die grinder much better. They are in expensive (about $19) run cool and have lots of power. Mine air grinder has colletts for 1/8 and 1/4 bits. Also the air grinder speed is controlable. Only problem is you need a decent compressor and tank. I first used one at the shipyard which has air at each stall. I liked it so much I got a 5 hp compressor with 15 gallon tank (I do use many other air tools now). Bob Austin Symbol 42 Pensacola, FL