130619 JerryW 14.5 inch back coring of mirror blank disk

Here's a photo of drilling a central hole in my 14.5 inch disk in progress.  This the back of the blank.  The coring will come within 3/16 of an inch of the front side.  The front side is ground to #120.  You can see a dam of oil based clay holding a water/grit mix while the coring tool turns at the drill press' slowest rate.  This is in Joe D's garage.  The blank is clamped in a custom wooden jig to prevent any motion.  The jig is clamped to the drill press' horizontal platform.

I had the tool machined out of soft steel, but any circular metal object can be used.  One common tool is an empty "tin" can.  [also another wider photo here: https://secure.flickr.com/photos/27241501@N03/sets/72157634222053744/ ]
Jerry