There are several ways to create a blank with end caps. Whichever way you use, the end caps have to be even or it sticks out like a sore thumb. The way I prefer is to create the entire blank before you drill it and it's the most common way I do it. It's very easy to create even end caps this way. That being said there are occasions where you need to glue the tube in first leaving equal lengths of the tube protruding from each end. Laser cut blanks come to mind because they are already drilled. I don't see many laser cut blanks that include segmenting, such as end caps. To that end, I created a simple little jig that helps me create the blank with even end caps. It's just a length of delrin rod that has a hole about 1 1/2 inch deep that a 1/2 inch length of delrin rod slips into. The 1 inch rod has 1/4 hole all the way through and on the opposite side I drill a hole that a connector nut press fit into. The 1/2 inch rod is threaded onto a threaded rod and just screws into the connector nut. I added a wing nut, thread locked on to give me an easy way to turn it along with a wing nut to lock it into place. Measure the wood part and the tube length, figure difference between the two, divide by two. That number is how deep the 1/2 inch rod is inset into the jig. I set that depth with calipers. Now when you glue the tube into the blank you just set it into the jig and the brass is perfectly even on both ends. After the glue sets you just make your end caps and glue them on. One of the pictures shows a blank I made the other day before my jig, I thought it was perfect and it wasn't even close. The pen was made using my jig and it came out perfect.