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DRILLING
Drilling is a cutting process that uses a drill bit to cut or enlarge a hole in solid materials. The drill bit is a multipoint, end cutting tool. It cuts by applying pressure and rotation to the work piece, which forms chips at the cutting edge. Drill bits are cutting tools used to create cylindrical holes. Bits are held in a tool called a drill, which rotates them and provides torque and axial force to create the hole. Specialized bits are also available for non-cylindrical-shaped holes.
A drill or drill motor is a tool fitted with a rotating cutting tool, usually a drill bit, used for drilling holes in various materials. The cutting tool is gripped by a chuck at one end of the drill and rotated while pressed against the target material. The tip of the cutting tool does the work of cutting into the target material.
Drills are commonly used in woodworking, metalworking, and construction and most "do it yourself' projects. Specially designed drills are also used in medicine, space missions and other applications.
The earliest drills were used by the ancient Egyptians. The drill press as a machine tool is many centuries old. It wras powered by various power sources over the centuries, such as human effort, water wheels, and windmills, often with the use of belts. With the coming of the electric motor in the late 19th century, there was a great rush to power machine tools with such motors, and drills were among them. The invention of the first electric drill is credited to Arthur James Arnot and William Blanch Brain, in 1889, at Melbourne, Australia.
There are many types of drills: some powered manually, others using electricity or compressed air as the motive power.
A drill press is a fixed style of drill that may be mounted on a stand or bolted to the floor or workbench. A drill press consists of a base, column, table, spindle, and drill head, usually driven by an induction motor. The head has a set of handles (usually 3) radiating from a central hub that, when turned, move the spindle and chuck vertically, parallel to the axis of the column. The table can be adjusted vertically and is generally moved by a rack and pinion. The table may also be offset from the spindle's axis and in some cases rotated to a position perpendicular to the column.
A drill press has a number of advantages over a hand-held drill:
Less effort is required to apply the drill to the work piece. The movement of the chuck and spindle is by a lever working on a rack and pinion, which gives the operator considerable mechanical advantage.
The table allows a vise or clamp to be used to position and restrain the work, making the operation much more secure.
The angle of the spindle is fixed relative to the table, allowing holes to be drilled accurately.
Задание :ответьте на во к тексту: (записать во и написать ответ на английском языке и перевести ответы на во письменно, как диалог)
1.What is drilling used for?
2. What is a drill bit?
3.What operations is a drill used in?
4.When was the first electric drill invented?
5.What main parts does a drill press consist of?
6.What advantages does a drill press have over a hand-held drill?

kola56    2   18.04.2020 00:39    3