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.
drill sizes in this chart for two reasons... Occasionally it is important to drill a hole that is a good fit on a wire for soldering purposes or for clearance purposes. Some drill blanks are used as rods in some mechanical engineering designs.