Need help replacing old drain

Hi, I'm in the process of installing a new, homemade shower pan (thanks to the help of other posts) but am still in a dilema of how to install the new clamping style drain. I currently have a regular drain (cup with grate) embedded in concrete. I would love to have some kinda simple adapter but fear I need to remove the old drain.
Some people recommended I just jackhammer the whole thing, trying not to break the drain pipe. Is there a safer way (i.e. chisel?).
Should I expect when I get down the 2-3" that the drain will simply unscrew from the existing pipe as well?
Thanks in advance.
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David Roberts wrote:

You'll have to supply loads more info. If it's iron pipe, it may be leaded into a cast iron fitting, just as one example. There are dozens of scenarios possible.
You might be able to Sawzall the pipe just above the concrete and add a Fernco No-Hub coupling to extend the pipe.
Maybe post some digital pics on a web site (Don't post to newsgroup).
Jim
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Okay, I can take some digital photos but there's not much to show as the pipe is still embedded in concrete. I don't know the type of fitting but the house was built in 1957, although I believe the shower was added later.
I can't sawzall the pipe above the concrete because it isn't protruding above the concrete.
So theoretically, I would chisel away/jackhammer the concrete around my drain below where it attaches to the drain pipe. Then should be able, thru observation, determine if it can be unscrewed. If not, then I will cut it, attach a coupler, then another piece of pipe that is perhaps threaded for my new drain yes?
The drains I've seen at home depot are plastic so I take it the thread is really the only way to mate plastic to metal.
thanks
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David Roberts wrote:
<SNIP>

You might try a masonry abrasive saw blade in a circ saw, if you can stand the dust. Plunge cut 4 slices around the pipe. Then chip out the remnants with chisel. You won't have to go very deep, just enough to get a coupling on.
Use a Fernco coupling (HD has them). Will connect steel pipe to PVC with no threads. I would definitely avoid going deep enough to find out what the steel pipe is connected into. I can almost guarantee a bigger project.
Jim
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Thanks Jim. I was thinking about using my circular saw. When you say avoid going deep do you mean say no more than 2"? I figured making a square around the drain, chiseling it, but thought I might still be challenging to get off the drain or rather determine if it was threaded but that seems to be the only way.
Does this Fernco coupling have some sort of glue with it? I didn't think there was an adhesive for metal to pvc.
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<SNIP>

The coupling has a stainless band and 2 "hose clamps"; no glue req'd.
Jim
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