How to drill square holes

[Bob-tx]

How to drill square holes and several other interesting mechanical principles.

[Robert Macy]

The Rouleau(sp?) triangle drill CANNOT drill a square hole ...exactly, because it cannot reach completely into the corners.

[mark]

Check out "rotary broaching"

[Jon Danniken]

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

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.

Jon

[krw]

Use a mortising bit/

[peter.bagwell]

Rotary broaching is a great way to make small square holes in precision machined products. Take a look at this video which shows internal and external forms: (the video shows hexagons but square holes are made the same way)

Also, see

for more information about the tools.