I made and finished a device using a 3/4 inch drill chuck, bought two sets of punches to use with it dedicated and on the shelf above to square the various sizes of pen blanks. The two sets imperial and metric should cover the range needed. The 12 inch sander I will use just for this. I have an adjacent 12 inch for general use. I will grab a pic later on. For ever it seems I have been mostly making Slimlines so I had used a mandrel shaft set in a square piece of wood, then made sleeves. I found the sleeves had a mind of their own and disappeared sometimes in the sawdust or elsewhere.
Peter..