Cut a short length of slimline tubing and glue it inside the centerband material, if your new material is wood. My experience has been that most woods need the extra support inside them in order to turn them to such small dimensions. You might get it turned okay but then it's liable to break once it's in use on the pen.
To make it move more easily you can sand away a bit of the brass interior of the tube.
This suggestion also applies to Orian if you're using glued up pieces. You might not need the tube if it's a solid piece of corian from the beginning. Then just drill your quarter inch hole and go for it.
What I want to know is whether one could make the tip pieces and the end pieces that go on the back ends of pens (traditionally called 'tassies') from wood or some other material?