For my newest creation, a steel pipe, I used:

A stainless steel nut that is for some reason smaller at one end. (Not tapered, it's like a washer is welded to the end of it)

A stainless steel hexagonal tube, with slightly rounded and tapered ends. It's meant to hold my punching bag up somehow, but my dad ended up not using it *shrugs*.

A microphone screen. My dad's been a singer for 20ish years, he has plenty of extra microphones. I just took tin snips to one.