Wegener also noted that the continents move up and down to maintain equilibrium in a process called isostasy. As an example he cited the sinking of Northern Hemisphere lands under the weight of continental ice sheets in the last ice age, and their rise since the ice melted some 10,000 years ago.
Drill that is fitted with a Pipe provides effective connection to the rig surface equipment or application with the bit and the bottom hole assembly for the purpose of pumping the Drill fluid to the bit.
The revolving vertical spindle of the drilling machine holds and drives the cutting tool. In order to use various sizes and shapes of drills in various machines three types of drill holding devices, which fit the spindle of the drilling machines, are used: the geared drill chuck, the drill sleeve, and the drill socket (Figure 6-22).