I've been trying to cut this inner sleeve using an air-hammer bit, but even with a 12# sledge, it wasn't working. This tool is going between the upper isolator (rubber mount) and the upper sleeve's flange to add some preload to the rubber.
It worked, and I was able to cut enough of the inner sleeve to release it. I was also able to remove the burrs & weld the nut back on so it can be reused.