[tsaksa]

I have used this technique for years to produce all manner of hole profiles, pentagons, hexagons, even triangles, that are significantly over sized for the drill bit being used. It works best using a very large diameter drill bit held in a small hand held drill. A badly sharpened drill bit works best, as does thin soft material that tends to produce a lot of drill chatter. By hand the technique is a bit difficult to reproduce. I seem to have the best luck getting them to come out with good sharp corners when I am overly rushed, and absolutely need round holes that are not over sized.

Tom