How do I cut a round 2" hole in a verticle 4" cast iron pipe?

Wouldn't you have to use an acetylene torch to do that sort of work?

How do I cut a round 2" hole in a verticle 4" cast iron pipe?
A much better way would be to cut in a 4 X 2" sanitary tee into that stack. Even if you could cut a 2" hole in the cast iron how would you connect anything to it? What do you want the hole to connect to? Regards, Tom