I am in the process of making an item for my saltwater setups, and have to thread the inside diam of a 3" socket joint (happens to be correct bore needed for my application and only needs threads) which are 13 tpi. My biggest problem is if I tighten the piece up in the chuck it distorts it. I ruined a bunch of pieces trying to find a sweet spot n chucking prressure with out distortin oor without having it slip. Even with light cuts its gone wrong. Perhaps I need to put it all away and give it a try on anaother day, unless someone can suggest something that may work to hold this piece in the chuck without distortion or slipping. I have played with super glueiing it, double faced tapes, but one thing I have not tried net is to glue two or three lugs on the outside of the piece I am turning and allow them to hold against the chuck jaws sides.........hmmmmmmmthat idea just hit me, is there anything else that may work?
PVC is neat to machine, but it can get awfull flimsey and such when chucked up.....