Foundation, Concrete and Earthquake Engineering

A Brief History Of The Drill

Drills with a percussive action (such as hammer drills, jackhammers or pneumatic drills) are usually used in hard materials such as masonry or rock. The drill bit is gripped by a chuck at one end of the drill, and is pressed against the target material and rotated. The earliest drills were probably bow drills. The hammer drill is similar to a standard electric drill, with the exception that it is provided with a hammer action for drilling masonry.

Types of Drill

A drill press (also known as pedestal drill, pillar drill, or bench drill) is a fixed style of drill that may be mounted on a stand or bolted to the floor or workbench. A radial arm drill is a geared head drill that can be moved away from its column along an arm that radiates from the column. The other end of the drill bit, the shank, is described in the drill bit shank article I wrote last week. Low spiral drills are used in cutting applications where high cutting speeds are traditionally used, and where the material has a tendency to gall on the drill or otherwise clog the hole, such as aluminum or copper. The drills have an extremely fast cutting tool geometry: no point angle and a large (considering the flat cutting edge) lip angle causes the edges to take a very aggressive cut with relatively little point pressure. The flutes of the drill bit body carry away the dust.


Slower speeds are also necessary for things such as polishing, finishing, and soft tissue drilling,so dental drills are typically equipped with secondary motors. Today's giant drilling trucks use steel cable, longsteel bits weighing up to several thousand pounds, and have rugged diesel engines which raise and lower the tools quickly andeasily--so that two men can drill hundreds of feet by themselves in a matter of days.

Tool Bits

Introduced by Unibit Corporation in the 1980s (formerly a subsidiary of Petersen Manufacturing Company and now part of Irwin Industrial Tools), step bits have been copied by other manufacturers since the patent expired. This is ideal for a bit for a hand tool. You never lose them, either - that DeWalt yellow shouts at you from across the room, across the lot or from under a pile of tools and offcuts.

Cordless Drills

For projects around my house it has plenty of power although, like every other cordless tool I have used, it needs a little more time drilling/driving through hard wood. The modern day CableTool drill uses the same technique as the percussion drill, but in much larger sizes. But the hand powered percussion drill, which was used to make the first wells in Asia, Europe, and the United States, is a time-tested tool that is easy to build and inexpensive to maintain.


You can see from this what DeWalt 18V drill-drivers have done and can do, and still I have not had the slightest problem, though they look pretty beat up now. The Dewalt DC925KB is a powerful 18 Volt combination power tool for heavy duty hammerdrilling and screwdriving applications. This review will help you decide which DeWalt 18volt tools to use for every situation. We deal with high-quality, popular brand names, which you've come to trust like DeWalt, Bosch, Ingersoll-Rand, and Chicago Pneumatic. The DeWalt cordless hammer drill comes in a half-inch size, offering plenty of power, an affordable price, and features worth the purchase. Well, trials showed that the DeWalt drill worked faster than Milwaukee's drills, and the battery lasted longer than other brand models. The DeWalt cordless hammer drill comes with two 36-volt batteries, a one-hour charger and a heavy-duty kit box. Now I have a whole lot of DeWalt HD 18V tools, because these two drill-drivers performed so well I was not afraid to buy into a lot of tools in the same line.

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