My wife and I have been renovating our powder room, primarily based around an 1932 American Standard cleat sink. I got a 17 gauge 1.5 inch brass p-trap which came with an unthreaded tailpipe. The tailpipe diameter is exactly the same size as threaded nut that was soldered onto the waste pipe, so it doesn't actually fit inside. Is there a way to connect these two pipes that doesn't involve cutting the old pipe then soldering on an expander or something?
ETA - the water pipe itself seems to be 1.5 inches, since 1.5 inch hinged wall plate fits around it.