Boring (mechanical)
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In machining, boring is the process of enlarging a hole that has already been drilled, by means of a single-point cutting tool, for example as in boring a cannon barrel. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole.
The term boring is also sometimes used for drilling a hole, especially with respect to tunnels and wells in the earth.
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[edit] Earth boring
Boring is used for a wide variety of applications in geology, agriculture, hydrology, civil engineering, and oil and natural gas industries. Today, most earth drilling is done in order to do one of the following things:
- return samples of the rock through which the drill passes
- access rocks from which material can be extracted
- access rocks which can then be measured
- provide access to rock for purposes of providing engineering support
[edit] The Kola Superdeep Borehole
In the 1970's and early 1980's the USSR attempted to drill a hole through the crust, to sample the Mohorovicic Discontinuity. The deepest hole ever drilled failed not because of lack of money or time, but because of the physics of rocks within the crust. The hole achieved approximately 12,000 metres depth, a depth at which rock begins to act more like a plastic solid than a rigid solid. The rock also approached temperatures of several hundred degrees Celsius, requiring that the drilling fluid was refrigerated before being sent to the cutting face of the drill. As the drill bits burnt out and were removed for replacement, the hole simply flowed closed, and the rock had to be re-drilled. Due to the temperature, the drill bits burnt out before achieving any headway. The hole was scrapped.
Further attempts at super-deep drillholes are planned by American consortia and further Russian attempts in Finland.
