In my last column, I wrote about bailers for cable-tool drilling. In this installment, I cover another basic part of the tool string: the drive clamps or drive blocks.
Just about every hole drilled, whatever the purpose, requires casing pipe. This pipe must be driven into the earth. We can make some hole out ahead of the casing but, by its own weight, it will only follow a few feet. In a few scattered locations, we might hit bedrock from the start. I know of areas just west of me with virtually no drift on top of the rock, perhaps as little as 6 inches. But, in most cases, we have to drive casing pipe through sand, clay and mixtures of both to get to the formation. We drive this pipe using drive clamps, a process where our drill rig performs like a pile driver.