guys i dont wanna sound like im a know it all, but that dont sound good. im a tool&die maker, i work with metals everyday. any joint in a piece of metal is a weakness. and alum is even weaker than most metals, alum is a alloy it wears very easy at rub and contact points. if you use metal thread, it will after time wear your insert out. then the wall thickness of your arrow will go. its just not worth the risk of putting the back half of your arrow through ya hand. i' ve seen takedwon arrows, but they were sleved, not inserted with thread. but still why ask for trouble, ive never had a reason for a takedown arrow. they just aint that long.
but this is just my opinon, but would hate to see someone hurt.

takecare, God Bless, Billy