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.
Nothing new to buy! There is very little set-up time when using a grinder for sharpening drill bits. Just put on eye protection, turn the machine on, and start sharpening. A bench grinder can also be used for scissors, lawnmower blade sharpening, and putting a sharp edge on other garden tools.