I’ve now got the aluminium rod pen down pat. I make a centre hole, run the rod further out and use a centre dog, and run a chunky cutting bit down the whole length of the piece, leaving a small chunk of rod inside the chuck. Then I run the rod further in, and drill out the part I have centred with a 1/4″ bit to the depth of about 1″. Then I reverse the rod and cut down the part that was in the chuck, adding a couple of notches so the tiny difference in thickness is not noticeable. Then I run the same bit across the end to flatten it off, and I’m done. I also, for extra points, remember not to leave the chuck keys in the drill or the main chuck, so I don’t die. That’s always a bonus.