Drill bit cuts a square hole

Originally published at: Drill bit cuts a square hole | Boing Boing


If you’re into this kind of thing, I highly recommend How Round is your Circle by Bryant and Sangwin. There’s an entire chapter on shapes of constant diameter that goes into detail about the neat tricks that Releaux rotors and other similar shapes can do – and it talks about not one but two different drills that drill square holes!

There’s a website with videos, too. (Warning: very 2003.)


@beschizza This is called a rotary broach. He made a kinda home-brew version that is simpler in design than commercial ones (which is on brand for Russian machining channels) but that’s what this is.


Thank you! updated


Yeah, I’ve only seen the kind that’s a single tapered head with an offset angle driven by a live spindle. This seems overly complicated, and the hole’s corners were pretty rough. But any time a Reuleaux triangle is used in a practical application, I’m happy.


The square hole drill bit I’ve seen was at the scene shop at my community college’s theatre dept. It was a woodworking square hole drill. Set up on a mortise and tenon machine it’s a round drill bit combined with basically a square chisel surrounding the bit. So it goes straight down in the mortiser and the round bit drills the hole and removes the waste while the chisels square off the corners.


90 degree angles granite rock.

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