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:
I think you are stretching it by trying to call a cam inside a box guide a
"gear box". :)
This link is interesting:
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.
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.
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
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?
-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
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