In many drilling operations a vertical hole is drilled, and then at some depth the drill is turned and the hole is drilled horizontally. How do they turn the drill (bit)? How abrupt a turn is it?
Not exactly what your looking for, but this should be the same fundamentally.
I was watching a show a few years back on the History Channel about the drilling of a subway in Singapore. To make bends in the subway, the body of the drill bit was cocked in very very small increments to make a large curve.
That’s kind of what I was thinking; that the bit can be controlled to cut to the side, and that the angle could cover hundreds of feet.
You can make pretty abrupt turns by putting a universal joint on the end of your vertical drill, and attaching a horizontal bit to the other side.
If the OP is asking about Oil drilling I too would be interested to know how they do it.
Seems they can be down thousands of feet and then set drill off at an angle. I doubt an ordinary universal joint would do give any directional control.
So how do they do it ?
I suppose they could also stick some sort of more complicated gearing mechanism on the end.
But then how would they get the drilling pipe in and out? It’s got to be curved hole, even if it looks sharply angled in a to-scale diagram. I’m guessing that they use a drill bit that’s cocked at an angle to the pipe to achieve the curve.