Water Well and Test Borehole Drilling Machines (click an image to start slide show)

Cable Tool -- original drilling method invented by the Chinese in 2,000 BC. Drills by lifting and dropping a drill bit, then bailing the cuttings. Casing is advanced with the drill bit by driving. Has the advantage of under-balanced drilling -- the fluid pressure in the borehole is less than the formation water pressure. This favors a clean borehole.