They do indeed really cut square holes. They’re called mortising bits. Like the other commentor stated, they’re basically a combination of a chisel and a drill. The drill does most of the work in waste removal while the square blades give you 90° corners.
One could also potentially consider a rotary broach to be a “square drill” (supposing that it is a square and not a hex or other shape).
3 points
Nah. Don’t sell yourself short. Your explanation is accurate and to the point.
1 point
Well thank you for the vote of confidence, but no, your explanation is much better; mine was basically a summary, while yours is in-depth
2 points
For those wanting to know how a rotary broach works https://youtu.be/IT8VXQEKzoo
It’s how the internal hex gets put into socket head cap screws
