After a little research (and making chucks) allow me to revisit this topic. Here are some chucks I made out of steel conduit from Lowes. I think they are half inch.
If you are looking for light chucks, I do not recommend steel conduit. Mines are hollow and definitely the heaviest pair in my collection. I do not use them inside because these are the kind of chucks to get away from you during a wrist roll and end up through the wall of the room you are in, the insulation, the wall of the next room over, and into the fishes tank sitting on the table.
You had it right from the beginning. A thin hollow aluminum rod will make perfect chucks. I got a pair I made from a red aluminum broomstick handle. Not my favorite color but they are extremely light. Just make sure that the aluminum isn't too thick. As an engineer, I do not recommend titanium. It costs more and in an ideal pure form, titanium is about twice as dense as aluminum (it's heavier). This might change with various grades of alloys but the fact remains, finding lighter aluminum is much easier.
As a craftsman, I recommend titanium only because titanium chucks would be pretty freakin badass.
Just go to a hardware store and check the aluminum conduit (if they have it). You might also want to check rods used for closet racks and other household racks. Or you can do like me and most other DIY chuckers and get a trusty old broomstick. Pick the lightest one, cut it up with a sawzall, pop two holes in it for your string, and you should be ready to rock!
