Create new part within the void of another part (mold)

I’m trying to create a new part within the void of an existing part. I’ve got a simple 2" PVC pipe with threaded ends and a threaded cap. I’m trying to create a new part that slides into the void of the pipe which I can then additionally model with some other features?

Here is the pipe.

Question? How do I use the pipe to “mold” my new part?

Here’s a way. Create a plane at the end of the pipe. Then draw a circle on that plane, equal to, or slightly smaller in diameter than your pipe. Then extrude the new pipe.

Thanks. That does make a new inner piece. But the top face doesn’t match the inside top of the pipe face formed by the cap and pipe. Thanks for trying to help me.

@SteSchmi thanks. Now this is something new I haven’t tried yet. I’ll give it a try and report back

Much thanks. That worked!

I was trying to extrude from the plane and do the subtraction all at once from the Boolean choice menu. When I finally extruded to a new body and then did the subtract operation, things started happening. Thanks for getting me back on track.