In addition to what Jim just posted, you would use a dead center/live center when turning with Turn Between Centers Bushings, TBC bushings, these are machined to tighter tolerances and will result improve your fit of the pen blank to the pen components.
These bushings are available now at Classic Nib and at LaserLinez (who machines these) Also, contact Brian Nikitas here on IAP for a custom turned set of TBC Bushings. These bushings will have a 60 degree cut in the rear for the centers to fit into.
Note: Some of these bushings are available with a hole drilled through for use on a mandrel in addition to between centers.