How to drill a square hole

[tigtorch]

   

[cidrontmg]

There's a recent (starting at 06-15-2013, 05:58 AM) thread at http://www.homemodelenginemachinist.com/f25/how-drill-square-hole-21123/
even their exact wording. Good Russian animation, but no sound     

[RichardShute]

For information the odd triangular blob is an example of a Reuleaux polygon. You can have such a shape with as many faces as you want, the commonest example in Britain is a 20p an 50p piece - that shape was chosen as it is considered least likely to jam in a coin machine. The 3 faced version is also used as the shape of the rotor in a Wankel engine. Trivial factoids.....

Richard

[PTsideshow]

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.