Clamp or screw.

We are preparing to tie into an existing cast iron 2 in stack with a new laundry drain. there used to be a laundry sink draining into it via an ABS trap but this is poorly situated for what we are doing.the question is this. My understanding is the best way to tie into the cast iron is to cut it and attach an ABS fitting with sleeves and clamps. But there is a place where a cast iron fitting is screwed in. My husband think the best solution is to remove that fitting and screw the abs fitting in its place. So what is the best solution?

If I hear you right, I would just screw a nipple into the cast iron stack and use a no-hub band to make the transition to ABS or PVC....
I don't like to connect cast iron via plastic threaded fittings.

If he can unscrew it and screw in a new adaptor I would do that.

I've seen plastic adapters get loose when threaded into cast iron or duram fittings and then don't hold their position........He can do it, but you can bet I wouldn't do it that way.

Well, all i can say is that when I thread one in, it's not going to move when I'm done, unless you have 18" pipe wrench on it.

That said, if I thread one in and it bottoms out then I do something different.

thanks, everyone, thats a lot of help

rusty pipes

just thought I'd share-- it all became moot when we started working on it, and the whole thing broke off in our hands, just above the floor and where the vent attached. both joints were rusted almost through. So we dug a hole in the slab, looked for solid pipe and clamped it.
We got to looking at other pipes, and are going to replace the kitchen drain-- looks like it is rusted almost thru in a couple places too. We want to finish off that basement, and dont want to be pulling down a wall in a couple years when that thing starts leaking. This pipe is plastered into the wall under the sink, and we cant pull that coupboard out, so wish us luck.

Luck has nothing to do with it but...... good luck.

Thanks Kellyb.........

How long do the joints last.

other than the fact that I was able to cut the cast iron pipe with a drywall saw, it went pretty well. Took only about 6 hours, thanks to what Ive learned hanging out here . One more question-- as I was connecting the new abs to the old cast iron with the sleeve/clamp thingys I picked up at home depo, I got to wondering about the life span/fail rate of those contraptions. It doesnt seem like a rubbery sleeve is going to have the life span of, oh, cast iron or ABS. Any insight?