Drilling square holes
I’ll start by clarifying that I don’t actually have a need to make square holes at the moment but I am facinated by these techniques. The maker of the above video Jacques Maurel also wrote an article for Model Engineer
Broaching
Broaching is a technique for turning a round hole into a square hole or a hex hole or for adding a keyway into a hole. A broach is a toothed tool that looks a bit like a rack or coarse