Connectiing abs to cast iron

I am remodelling a bathroom and I have to reposition the toilet. In the process of removing the old flange I have discovered that the 3" copper pipe was set inside the cast iron pipe.
Is there a product in abs that I can use to connect to the cast iron without having to modify the cast iron?
Can I just push the abs in where the copper came out of?

They make coupling like this to join pipes.
They come in cast sizes, ABS sizes and copper sizes.
Also transition sizing from ABS to copper.

Just be sure you get a "banded coupler" like the one in Terry's reply. They also have Fernco couplers that are just neoprene sleeves with two clamps. These are not OK for what you want to do.

Donel said:

... just push the abs in where the copper came out of?

Click to expand...

The outside diameter (OD) of the copper and the ABS are not the same size, so the hole you left -- if you took the copper out -- is not the same.

Measure the OD and ID of whatever you still have left intact, whether it's a bit of 3" copper, a bit of Cast pipe, or a female threaded Cast SanTee fit, or whatever. Knowing that will determine what you get next. With a banded coupling you are up and running in no time. (The band is the support in the middle visible in the picture above, preventing the flexible material from moving around too much over the years as pipes move slightly with the season).

fair warning about plastic drains: they make more noise than Cast or copper. Flushes will sound louder in the room below. Consider wrapping it tight for sound insulation.

david