Drill square holes in metal?

http://www.wimp.com/squareholes /
I'm having trouble wrapping my remaining brain cells around this one.
How does it do that?

Richard wrote:
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I drill triangular holes.

On 10/3/2011 10:10 PM, Beryl wrote:
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Ok, I'll be your Huckleberry.
How?

Richard wrote:
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I don't know why, it just happens.
Your video link is outside my reach, but maybe the drill is really a broach?

Beryl wrote:
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We've all seen triangular holes from standard jobber bits. The bit flexes a little while drilling causing the hole to resemble a Reuleaux triangle.
--Winston

On 10/3/2011 11:20 PM, Winston wrote:
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I don't think that's the deal here, Winston. It's making nice square holes, albeit with radiused corners.
the few brain cells I have left are complaining madly about that.

Richard wrote:
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I was addressing your 'Huckleberry' question about the triangular holes. The two are related. The cutters in both cases oscillate as well as rotate. In the 'jobber drill' instance, the oscillation occurs as the long, spindly bit ricochets around the center, bouncing off the walls of the hole.
The square cutter does have a gearbox to carefully control the additional displacement of the cutter to create a square hole. See how:
http://www.youtube.com/watch?v=L5AzbDJ7KYI&feature=related

--Winston

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I think you are stretching it by trying to call a cam inside a box guide a "gear box". :)
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This link is interesting:
http://web.mat.bham.ac.uk/C.J.Sangwin/howroundcom/roundness/applications.html
It shows that with a slightly different shape, you can make it trace a true square instead of one with rounded corners. But the drawback, is that only one point is tracing the square, instead of three, so you could only have one cutting edge using that technique.
The original link on this thread seems to be cutting corners that are more square than a standard Harry James Watts Reuleaux triangle drill.
If you look at the drill at the opening of the video it looks far more triangular with flatter sides and truncated corners so maybe they figured out yet another cam shape that does a better job? The noise it makes when drilling however makes it sound like it's a box cam flapping around so it doesn't look like they used special gears to do the work.
http://www.wimp.com/squareholes /

Curt Welch wrote:
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Should I have said 'gear in a box'? :)
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Yes but still less time in handwork to sharpen up the corners if that is necessary.
Very cool. Thanks!
--Winston

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Doesn't Mazda use those?
-- Worry is a misuse of imagination. -- Dan Zadra

On 10/3/2011 11:17 PM, Beryl wrote:
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I don't think so....

Richard wrote:
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From the Reuleaux Triangle link you posted, "Because it can be rotated inside a square, as illustrated above, it is the basis for the Harry Watt square drill bit."

On 10/4/2011 12:24 AM, Beryl wrote:
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yeahbut...
I still think it implies a gearbox inside the drill bit.

On 10/4/2011 12:40 AM, Richard wrote:
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A 3-tooth gearwheel on the drill chuck, engaging the inside of a stationary (fixed) 4-tooth inside gear.
The drill motor in this instance only makes the drill "orbit"--the motor does not spin the drill directly, the gear engagement does that.
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Now MY question is,,,,, can you drill different-sized holes with one of these setups? Or is each head just fixed to use one bit, to make one size?,,,,
If it was adjustable at all, I'd think the range would need to be kept pretty small. Like maybe 1/4-inch to 1/2-inch?

On 10/4/2011 4:08 AM, DougC wrote:
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-Unless the whole thing is not just CNC, with servos controlling the motions. Which I think would be more likely with a modern setup. That way you could drill holes with any number of corners you wanted, down to three corners....

Richard wrote:
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Check these out too:

http://www.youtube.com/watch?v=9qEhyQfbImY


http://www.youtube.com/watch?NR=1&v=L5AzbDJ7KYI


http://www.youtube.com/watch?NR=1&v=JeIi04JoAoo

Richard wrote:
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Watch the collet area REAL close. Notice that it has LOT of motion. http://mathworld.wolfram.com/ReuleauxTriangle.html This shows how it works.