I have a two inch cast iron pipe w/cup coming up from a concrete floor. There used to be a connection at the cup for a sink drain. That piece was broken by my handy man and subsequently removed by me. Now I need to cut off the cup to facilitate repair using ABS part with rubber connections to drain and vent. A chain break does not fit between the pipe and the wall; there is no room for a reciprocating saw; so I am considering a 9" angle grinder operated with the cutting wheel facing up. How do I keep the cup from pinching the cutting wheel or flying out when it is cut through? I don't even like having the wheel facing up, so I might cut lower on the pipe to avoid the cup interfering with the grinder body. Any help will be appreciated.
Remember, cast iron is brittle. A chain-breaker does not actually cut it, it cracks and separates it. You can use the same principle: use the angle grinder make a groove to weaken material around the perimeter of the material right where you want it to break. Then allow the grinding wheel to penetrate all the way through at only a single spot (a 1/4" or so). Then use a regular cold chisel to finish the job: Drive the chisel in at a tangent, following the groove you just cut. The wedge shape of the chisel will lift the cup up and away from the pipe, and like cutting glass, it'll snap right where you weakened it.
I've done it many times, and it only takes a few minutes.
I think the best way to do it is using a reciprocating saw (which most folk call "Sawzall") and a diamond blade specially purposed for cast iron. At least that is what I used successfully to cut my cast iron pipe. Chances are low you'll find those blades at a big box store, I got mine at a specialty pluming store.