percussion boring
percussion boring Drilling with a chisel-shaped bit which is repeatedly struck against rock to form a hole. It produces very fine debris, which can be washed away by drilling fluid. If only the drill bit can oscillate up and down to produce the percussive effect, the drilling equipment is called a ‘down-the-hole hammer’. If the whole series of drilling rods and bit are oscillated from outside the drill hole, the equipment is called a ‘drifter’. See DOWNHOLE HAMMER DRILLING.
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Digital Equipment Corp , 146 Main Street
Maynard, Massachusetts 01754
U.S.A.
(508) 493-5111
Fax: (508) 493-8780
Public Company
Incorporated: 1957
Employees: 113,800
Sales: $1… Chassis , chassis •bassi, Brassey, brassie, chassis, gassy, Haile Selassie, lassie, Malagasy, Manasseh, massé, massy, sassy, Tallahassee •Cotopaxi, maxi, taxi,… Emc , EMC Abbrev. for electromagnetic compatibility. The property of equipment to work satisfactorily in an environment with other equipment. All pieces of… Trachyte , trachyte Fine-grained volcanic rock of the alkaline series of intermediate rocks. Trachyte is the volcanic equivalent of syenite.
trachyte gritty vol… Igneous Rocks , Igneous rocks are formed by the cooling and hardening of molten magma. The word igneous comes from the Latin word igneus, meaning fire, and there are… Aphanitic , Aphanitic
Crystalline rocks with mineral grains that cannot be distinguished from one another without magnification have an aphanitic igneous texture…
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percussion boring