I will have a task to make some lens cells from MIC-6, 1.125 thk x 8.5 OD, with a center bore about 6.22 ID. I would like to be able to remove the center slug as a chuck rather than turning it into chips. Trepanning through is always high-rish in my experience, but just wondered if anyone has better suggestions. Rotabroach as hole saw crossed my mind, but I imagine that's an expensive tool, and may not be efficient on a BPort mill. Any suggestions welcome.