using aluminum poles and make 'inserts' out of a 'JB Weld' type epoxy you might want to try 'molding' the the threads right in. If you can rig a jig of some sort to hold the bolt [coated w/ release agent, of course] centered in the end of the tube with a nut [or two, depending on the length of the insert] positioned on the bolt at a location that will place it near the center of the insert [the nut(s) will become part of the 'insert' and add some actual metal threads inside of it]. I've used a similar technique making 'all-terrain' feet for a G.E.M. tripod [big rubber-covered composite feet that screw up towards the end of the tripod leg to reveal spikes].