Back when I was in the first semester of machine shop for tool and die makers we had to drill a square hole in a 1" CRS rod about 1 1/2" long I pretty sure I still have it around here. We did it in a lathe the collet chuck arraignment would hold assorted sizes and shapes of stock.
You drilled a hole slightly smaller then the finished version.
Then you picked the reamer with one less blade then the finished hole,
Like in the animi there was a face plate that was the shape and size of the finished hole.
It was some amazing stuff for a kid back in 1965, and the instructor used that as one of his what they call now"thinking out side the box" exercises.
He had an octagon, hexagon, and a triangle one I wanted to do one of each but never got too.
I f I can find it I will take a photo.
