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 bits are cutting tools used to create cylindrical holes, almost always of circular cross-section. Drill bits come in many sizes and have many uses. Bits are usually connected to a mechanism, often simply referred to as a drill, which rotates them and provides torque and axial force to create the hole.
Refer to a technical publication for the exact measurements for hole size. For example, if you want to use a 1/4-20 screw then you must use a #7 drill bit. Your set of taps may also state the appropriate hole size to use with each tap. tap cuts threads on the inside of a hole, to accept a machine screw or bolt. Taps can also be used to restore an internal thread that has been damaged or to cut a new, larger thread in the case of severe damage or stripping. Ad.