I seriously recommend that nobody use a bonded abrasive type wheel or disc on the aluminum tailpiece at all. I manage a design/fab shop and know that ferrous metals grind and cut easily with abrasive discs, and the pieces are thrown in the form of sparks, this dissipates heat. Non-ferrous metals clog and build up on abrasive wheels, building heat beyond what the disc can take, causing it to explode. Already having centripetal force, this can cause extremely painful damage to your tender meat sack of a body. Use a BLADE tool of some kind hacksaw, bandsaw, sabersaw, when rough cutting Aluminum. That's my professional recommendation.