On Thu, 12 Apr 2012 10:18:10 -0700, "Jon Danniken"
wrote:

Bob-tx wrote:
How to drill square holes and several other interesting mechanical
principles.

http://www.youtube.com/watch?v=L5Azb...eature=related

http://www.youtube.com/watch?v=9qEhy...eature=related

1. Mark the square
2. Mark the center
3. Drill a round hole
4. Take a triangle file to open up the corners

Use a mortising bit/

This works well, and I use it in metal whenever I want to use a carriage
bolt. This would obviously be too slow for production, though.