Made a bunch of these some years ago, in aluminum, with the plan of putting together a new type of cleaning kit. The idea did not take off but I think I have some adapters stored. I will look and let you know. They are threaded rod externally 5/15-27 tpi and internally are 4mm X0.8, it is a two piece affair internal and external rod. From what I see 8-32 is equivalent to metric 4X0.7 pitch.