On a much smaller scale than drilling for oil, such as in placement of
underground data or power cables or even water lines, a spoon shaped bit is
often used. A locator above grade can detect where the bit it, and if they
stop rotation and just push it for a ways, it will turn away from the bottom
side of the spoon. Then they can start rotation again and continue in a
straight line. Pretty common around places anymore for this type of stuff.
Much cheaper and faster than digging up a street or runway just because you
need to get some cable or pipe under it. They bore where they need to go,
and then when they start extracting the drill string, they can pull pvc or
poly pipe back through the hole they just bored.


wrote in message
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Oil rigs seem to be capable of drilling holes inches in diameter
and thousands of feet deep. They can keep these holes amazingly
straight or deliberately curve them.

How do they do this and what does the drill head look like?

Jim