A modern core drill is a drill specifically designed to remove a cylinder of material, much like a hole saw. The material left inside the drill bit is referred to as the core.
Core drills used in metal are called annular cutters. Core drills used for concrete and hard rock generally use industrial diamond grit as the abrasive material and may be electrical, pneumatic or hydraulic powered. Core drills are commonly water cooled, and the water also carries away the fine waste as a slurry. [1] For drilling masonry, carbide core drills can be used, but diamond is more successful when cutting through rebar. [2]
The earliest core drills were those used by the ancient Egyptians, invented in 3000 BC. [3] Core drills are used for many applications, either where the core needs to be preserved (the drilling apparatus used in obtaining a core sample is often referred to as a corer), or where drilling can be done more rapidly since much less material needs to be removed than with a standard bit. This is the reason that diamond-tipped core drills are commonly used in construction to create holes for pipes, manholes, and other large-diameter penetrations in concrete or stone.
Core drills are used frequently in mineral exploration where the drill string may be several hundred to several thousand feet in length. The core samples are recovered and examined by geologists for mineral percentages and stratigraphic contact points. This gives exploration companies the information necessary to begin or abandon mining operations in a particular area.
Before the start of World War Two, John Branner Newsom, a California mining engineer, invented and patented a core drill that could take out large diameter cores (>5 ft.) up to 10 feet in length for mining shafts. [4] This type of shaft-sinking drill is no longer in use as it was cumbersome, prone to jamming with cuttings, thus slow compared to conventional shaft sinking techniques, and only worked effectively in soft rock formations. Modern shaft-sinking technology accomplishes the same faster and at a much cheaper cost.
Core drills come with several power choices including electric, pneumatic, and hydraulic (all of which require power sources, such as a generator).
Wireline core drilling is a technique used to extract the core without having to retrieve the entire drill string of rods, which generally only needs to be retracted when the hole is finished or the drill bit must be replaced. Drill rod extensions are added at the top as required to extend the string as the hole gets deeper. The core sample is carried by an inner tube locked in place in contact with the drilling head, To recover the core, the drive system is disconnected, opening the top of the uppermost drill rod. A tool called an overshot assembly is lowered at the end of a wire and pumped down the string with water pressure. When it reaches the sample tube, it locks onto the top, and using the retraction winch to apply tension to the wire unlocks the sample tube from the drill head and retracts it and the core sample within it to the open top end of the drill string, where it can be removed before returning the sample tube down the drill string to lock back onto the cutting head. This is particularly useful for drill holes more than 30 ft deep as otherwise the whole string of rods had to be removed to recover the core, then re-inserted to drill deeper, and repeated. Removing all the rods every 30 feet to recover the core was time consuming for deep holes required for mining and mineral exploration, some of which may be 1,000 ft deep or more. This method greatly reduced the time required to drill a hole, and thus its cost, which increased the use of drilling and decreased the use of shaft sinking as a means of mineral exploration. It is also quite useful if there is a high risk of the hole walls collapsing when the drill tube is retracted, so it is suitable for most soil types, and to depths of 1000 m. Several diameters are available. [5]
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In petroleum exploration and development, formation evaluation is used to determine the ability of a borehole to produce petroleum. Essentially, it is the process of "recognizing a commercial well when you drill one".
A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water, other liquids, or gases. It may also be part of a geotechnical investigation, environmental site assessment, mineral exploration, temperature measurement, as a pilot hole for installing piers or underground utilities, for geothermal installations, or for underground storage of unwanted substances, e.g. in carbon capture and storage.
A drill bit is a cutting tool used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation. The drill will grasp the upper end of a bit called the shank in the chuck.
A drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person and such are called augers. Drilling rigs can sample subsurface mineral deposits, test rock, soil and groundwater physical properties, and also can be used to install sub-surface fabrications, such as underground utilities, instrumentation, tunnels or wells. Drilling rigs can be mobile equipment mounted on trucks, tracks or trailers, or more permanent land or marine-based structures. The term "rig" therefore generally refers to the complex equipment that is used to penetrate the surface of the Earth's crust.
A hammer drill, also known as a percussion drill or impact drill, is a power tool used chiefly for drilling in hard materials. It is a type of rotary drill with an impact mechanism that generates a hammering motion. The percussive mechanism provides a rapid succession of short hammer thrusts to pulverize the material to be bored, so as to provide quicker drilling with less effort. If a hammer drill's impact mechanism can be switched off, the tool can be used like a conventional drill to also perform tasks such as screwdriving.
A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The hole made for the core sample is called the "core hole". A variety of core samplers exist to sample different media under different conditions; there is continuing development in the technology. In the coring process, the sample is pushed more or less intact into the tube. Removed from the tube in the laboratory, it is inspected and analyzed by different techniques and equipment depending on the type of data desired.
In geotechnical engineering, drilling fluid, also known as drilling mud, is used to aid the drilling of boreholes into the earth. Used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells.
A hole saw, also known as a hole cutter, is a saw blade of annular (ring) shape, whose annular kerf creates a hole in the workpiece without having to cut up the core material. It is used in a drill. Hole saws typically have a pilot drill bit (arbor) at their center to keep the saw teeth from walking. The fact that a hole saw creates the hole without needing to cut up the core often makes it preferable to twist drills or spade drills for relatively large holes (especially those larger than 25 millimetres. The same hole can be made faster and using less power.
A raise borer is a machine used in underground mining, to excavate a circular hole between two levels of a mine without the use of explosives.
A diamond tool is a cutting tool with diamond grains fixed on the functional parts of the tool via a bonding material or another method. As diamond is a superhard material, diamond tools have many advantages as compared with tools made with common abrasives such as corundum and silicon carbide.
Exploration diamond drilling is used in the mining industry to probe the contents of known ore deposits and potential sites. By withdrawing a small diameter core of rock from the orebody, geologists can analyze the core by chemical assay and conduct petrologic, structural, and mineralogical studies of the rock. It is also often used in the geotechnical engineering industry for foundation testing in conjunction with soil sampling methods. The technique is named for the diamond encrusted drill bit used.
A down-the-hole drill, usually called DTH by most professionals, is basically a jackhammer screwed on the bottom of a drill string. The fast hammer action breaks hard rock into small cuttings and dust that are evacuated by a fluid. The DTH hammer is one of the fastest ways to drill hard rock. The system is thought to have been invented independently by Stenuick Frères in Belgium and Ingersoll Rand in the USA in the mid-1950s.
Boring is drilling a hole, tunnel, or well in the Earth. It is used for various applications in geology, agriculture, hydrology, civil engineering, and mineral exploration. Today, most Earth drilling serves one of the following purposes:
Boart Longyear is an international mineral exploration company founded in 1890 in the United States. It is headquartered in Salt Lake City, Utah, with regional offices and operations in the Asia-Pacific region, North and South America, Europe, and Africa. The company provides mineral exploration services and drilling products for the mining industry and also has a presence in drilling water exploration, environmental sampling, energy, and oil sands exploration. As of 2018, it employed more than 5,000 people.
Orex Exploration is a former Canadian gold mining company that conducted exploration work on mining properties it owned in the Goldboro and Guysborough County areas of Nova Scotia. The properties owned by Orex were the sites of the former Boston Richardson Mine, Dolliver Mountain Mine, West Goldbrook Mine, and East Goldbrook Mine which operated between 1892 and 1912. Headquartered in Rouyn-Noranda, Quebec, the company was founded in 1987 and raised funds for exploration work, in part, by issuing stocks traded on the Montreal Stock Exchange and then the TSX Venture Exchange. It became a subsidiary of Anaconda Mining Inc. after Anaconda acquired the company in a stock swap deal in 2017.
An annular cutter is a form of core drill used to create holes in metal. An annular cutter, named after the annulus shape, cuts only a groove at the periphery of the hole and leaves a solid core or slug at the center.
A magnetic drilling machine is a portable drilling machine with a magnetic base. It can use twist drill bits, annular cutters, milling cutters, and other rotary cutters. With suitable bits it can also tap threads, ream, and countersink. Its combination of a stable magnetic base and low RPM help resist or reduce torque forces created by large diameter bits. Magnetic drilling machines with reversible motor and variable speed controls can also perform operations like tapping, countersink and reaming. A magnetic drilling machine with a cross table base can also perform light milling.
Ice drilling allows scientists studying glaciers and ice sheets to gain access to what is beneath the ice, to take measurements along the interior of the ice, and to retrieve samples. Instruments can be placed in the drilled holes to record temperature, pressure, speed, direction of movement, and for other scientific research, such as neutrino detection.
Scientific ice drilling began in 1840, when Louis Agassiz attempted to drill through the Unteraargletscher in the Alps. Rotary drills were first used to drill in ice in the 1890s, and thermal drilling, with a heated drillhead, began to be used in the 1940s. Ice coring began in the 1950s, with the International Geophysical Year at the end of the decade bringing increased ice drilling activity. In 1966, the Greenland ice sheet was penetrated for the first time with a 1,388 m hole reaching bedrock, using a combination of thermal and electromechanical drilling. Major projects over the following decades brought cores from deep holes in the Greenland and Antarctic ice sheets.
A Rail Drilling Machine is a type of portable drilling machine specialized for drilling holes in rails. Rail Drilling Machines are also popularly called as Rail Drills, Portable Rail Drill, Rail Core Drilling Machines, etc.