Depends on many factors. Sometimes it'll fit, sometimes not. If the pieces are small, you put the inner in the freezer for a few hours and heat the outer with a torch or heat gun, then assemble them quickly.
I'm doing this to lengthen my tie rod. 1.25 DOM, 0.250 wall, adding in a new section and running 0.75 solid rod through it all. I don't anticipate a major problem. Your mileage may vary, though.