There pretty simple Dan. Here's what I do... Drill a hole in a scrap piece of wood, just smaller than the outer diameter of the pen top piece. Set it upside down over the hole and tap out the stock material with a punch. Then glue a piece of the blank or material you want to make the custom finial out of to a 3/4" square by 2" piece of wood. I use epoxy and let it cute over night. I put the small block in my Nova chuck with the glued on material sticking outward. I turn the material to the proper diameter, measuring with calipers so I don't have to take the block out of the chuck, and then sand and micro mesh like usual before using a small cut cut off tool to part it off about a 1/4" back. I use a very small old standard screw driver that I filed to a point on the belt sander. As it gets close, it will fall off leaving a small stem, which will drop in the hole of the cap piece helping to center it in place. Then I use epoxy and glue it in place. You can polish it on the Buffon wheel after the epoxy dries. I'm sure others will have easier ideas but this is what works for me.
