Broken 4" cast iron toilet drain pipe

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Detroit Michigan
Greetings from Michigan.
This should have been an easy DIY project, but I had to complicate things.
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Pearl Wilson

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Welcome! How can I help with your plumbing question?
The cast iron flange on my 4" toilet drain needed to be replaced. (I rather not say why). I removed all of the packing around the outside of the pipe, which in hind sight, I may not have needed to do. I purchased an Otey cast iron screw in flange. I lubed the threads, which I saw on some videos, and inserted it into the pipe. Started screwing and, after screwing in a few turns, got too hard to screw any more. I removed it and started over multiple times, with no success. Finally, i pounded it with a rubber mallet thinking the result would be the same as screwing it. Big mistake. A part of the iron pipe broke off to a depth of about 4". A clean break. Just one piece, no fragments. What can I do, besides call a plumber? Here are some thoughts I had.
A) Since I can put the piece back in, I can apply pressure from the outside, and it stays on perfectly. I thought if I filled the void around the pipe with cement, let it dry, then clean the inside of the pipe, apply a layer of epoxy, let it dry, then put in a different type of flange.
B) insert some kind of liner 6"-8" long into the pipe and fill the void around the outside of the pipe with something. All I could find online was repair to a much deeper break or crack. Can you please advise me? I would say i have above average mechanical skills.


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