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.
Tip forbeginners: 15 out of the 1to60 number drills are of no use for tapping, reaming, interference fits etc. Also most of those used for tapping any BA size are generally also a clearance drill for a two sizes smaller thread.