Drilling a Square Hole

Ask any woodworker if he can drill a square hole, and he'd say that of course ... with a hollow square mortise chisel & bit. But that's kind of cheating: it's basically drilling a round hole and chiseling the rest to make the square hole.

But did you know that there is a way to actually drill a square hole? With a Harry Watts square drill bit (named after its inventor, who patented it back in 1917). Here it is in action:

Confused? Here's a neat animation that shows what exactly is happening (hint: the bit is shaped like a Reuleaux triangle):

Pretty nifty, huh?

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Newest 5 Comments

Jolly, I never said it wasn't clever. I was just furthering the conversation in a positive manner, by adding some substance to the topic of discussion, namely that I would be surprised if this could be done with a hand drill, as suggested by the second image.

It was more a matter of a technical observation, and I certainly welcome comments from any craftsman with more experience in such things than I have.

Will L certainly added much more information, even though he didn't address the point that I had raised. Although his comment may appear negative, he is simply adding more detailed and technical information - information that I found instructive.

Since you didn't appreciate either comment, I'll oblige you: Wow, that's an awesome drill. Square holes! Cool! WTF. LMAO. Square holes FTW!

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@Will L & @ted so what? It's still pretty damned clever.

I'd reach for the plasma cutter every time, but then I don't have to do small holes.
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First of all, those holes were all hogged-out first by a standard bit.

You can also see the shank oscillating viz the cutting-bit center.

On a normal drill, the shank is obviously perfectly on-center.

Then your rotating-triangle can just notch out the corners.

-Still, -VERY similar to what a woodworker's bit does.

And quite simple to a Rotary Engine in a Mazda RX-8
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