I turn pens for fun, but drilling the hole in the blank was always a hassle. But aligning the drill exactly on center of varying stock thicknesses requires resetting the jig. There had to be a better way. There is!
My 4-jaw chuck on the lathe head and a Jacobs chuck in the tail stock makes a perfect bore every time. I don’t even lock the tail stock, just slide it. I position the pen blank in the chuck and close the jaws enough to hold it. Slide the tail stock in so the brad pointed bit hits the marked center on the blank, and clamp the jaws.
The only requirement is the blank be square, an easy job with the table saw if required.