My plumber is having a hard time cutting out the drain pipe to our new t.I. commercial location. When we dug out the concrete to lay out our pipes to connect the main drain pipe we saw a hole about 2" diameter on the top side. The plumber tried to cut it and it keeps breaking off.
What tools is he supposed to be using? What happens if it keeps breaking?

IF he breaks it to far ,he will have to use 2 special rubber boots to repair the line so there is no leaks. He can get or rent a special type of cutters used only for cast iron, they look like a big pair of plyrs, with a chain on them.. or he can use a skilsaw with a special blade for cutting cast iron. About breaking off too much, if he does then as I startedat the beginning. He will have to cut out enough to use the rubber boots ,made for the size cast you have and use a piece of pvc (3or 4 "), the rubber made to go from cast to pvc on each end.