When I saw the title of this video, I thought I knew what to expect -- a mortising bit in a drill press. This type of bit has a round drill bit that is trapped inside of a hollow square chisel. As the drill bit bores the hole, the square chisel is forced down, removing the thin corners that remain around its circumference. I've always wanted one, but have yet to find an excuse to buy one.
That's not what this video shows at all. This tool really does drill a square hole! OK, so the corners and ever-so-slightly rounded, but this is still a mind boggling concept. There are plenty of videos like the one below on YouTube showing people using this technique to drill square holes in metal. That's not something you can do with a mortising bit. This one was apparently described in the November 2006 issue of Model Engineer Magazine.