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Core Drilling Equipment The Drill String
1.Which are the main components in a drill string?
(1) Diamond core bit
(2) Reaming shell
(3)  Core barrel
(4) Drill rod
(5)  Water swivel

2.Describe the two core drilling standards.
The European standard which is based on metric dimensions is generally called the CMS standard and the US standard which is based on British units is generally called the DCDMA standard. Both systems consists of a series of drill hole dimensions and there are a set of drilling tools adapted for each such dimension.

3.Why is it not suitable to combine drilling tools from different standards?
(1) There are different types of threads.
(2) The dimensions do not fit.

4. What do we mean when we say that the drilling tools have a telescopic fit?
The following example will illustrate what we mean with telescopic fit. Drilling through the overburden down to solid rock has been done with casing 84/77 which is a standard CMS casing tube with 84,5 mm outer diameter and 77,5 mm inner diameter. The casing tube is equipped with a diamond impregnated casing shoe. The casing will be left in the hole. Drilling in solid rock is done with a 76 mm core barrel equipped with an impregnated diamond core bit and a reaming shell. The outside diameter of the core bit is 76,5 mm and the outside diameter of the reaming shell is 76,8mm and thus the core barrel, core bit and reaming shell will pass through the 84/77 casing tube. At a depth of 100 meter the drill hole runs in to a very broken formation and the hole must be cased with a 74/67 casing tube with an outside diameter of 75,5 mm and an inside diameter of 67,5 mm. This casing fits in the hole drilled by the 76,5 mm core bit on the 76 mm core barrel.When the 74/67 casing string has been installed in the drill hole the drilling can continue with a 66 mm core barrel which fits in the 74/67 casing.

5. What do the letters NWT stand for?
(1) N is the outer diameter
(2) W describes the group of tools for which the core barrel can be used.
(3) T describes the design of the core barrel

Core drilling bits
1. With what type of cutting devices can a core bit be armed?
a. TC (Tungsten Carbide)
b. PDC (Poly-Crystalline Diamonds Composite)
c. Natural diamonds
d. Synthetic diamonds

2. Which types of core bits are primarily used for geotechnical investigation drilling and for which types of geological formations are these drill bits intended?
ü Bits armed with TC or PDC are usually used for geotechnical core drilling in soft formations such as soil, softy shale, clay and very soft sedimentary formations.

3. Mention two characteristics of a diamond which make the diamond suitable for cutting hard rock?
ü The hardness of the diamond. A diamond is the hardest known naturally occurring mineral.
ü The very high coefficient of thermal conductivity.

4.Why can a TC bit not be used for drilling in granite?
ü The coefficient of thermal conductivity is too low.

5. What types of diamond bits are used in core drilling? Describe the difference between these diamond core bits
ü Surface set diamond bits and impregnated diamond bits.
- A surface set diamond bit is dressed with one layer of natural diamonds
imbedded in the envelope surface of a hard matrix.
- On a impregnated diamond bit the matrix is thoroughly impregnated with small diamonds, much smaller than the diamonds used in a surface set bit.

6. Which are the advantages with an artificial diamond as compared to a natural diamond?
ü The technique for manufacturing synthetic diamonds has had a fast development during the last decades. Today the synthetic diamonds are superior to the natural diamonds both in terms of life length and cutting ability.
ü Another advantage with the synthetic diamonds is that these can be given special qualities required for core drilling. The synthetic diamonds can thus be “tailor made” to suit drill bits intended for different types of rock. Brittleness, grain size and geometry are three important characteristics that can be “tailor made”.

7. What does a gradual graphitization of a diamond mean?
ü The diamonds looses their hardness and thus their ability to cut the rock.

8. In which units do we measure the weight and the size of a diamond?
ü The weight is measured in Carats. One carat is 0,2 grams
ü The size of a diamond is measured in stones per carat (SPC).

9. For which geological formations are the surface set diamond bits primarily intended?
ü Soft to medium hard formations

10. When is a surface set diamond bit consumed?
ü When all the protruding diamonds are blunt and worn.

1.Describe the design of an impregnated drill bit.
ü As the name implies the matrix in an impregnated diamond bit is thoroughly impregnated with small diamonds, much smaller than the diamonds used in a surface set bit. The diamonds used in impregnated bits are almost only artificial diamonds. Natural diamonds can be used as so called kicker stones who’s task is to keep the nominal diameter of the bit.

2. What does free cutting or self sharpening of an impregnated diamond mean?
Describe this process
ü The diamonds cut until they are worn
ÜThe matrix erodes and looses it’s grip on the worn diamonds
ü New sharp diamonds are exposed
ü These new diamonds cut the rock until they are worn
ü The matrix erodes and looses its grip on the worn diamonds
ü Etc, …

3. Which are the advantages of an impregnated diamond core bit as compared to a surface set diamond core bit?
ü A larger area of application as concerns geological formations
ü A more robust design that can handle drilling in broken and fissured formations
ü Can handle rough treatment
ü Will drill longer and faster in hard formations

4. Which properties of the rock have an influence on the choice of a suitable diamond drill bit?
ü Hardness: which is groped into soft, medium hard, hard, very hard and ultra hard rocks.
ü Grain size: which is groped into fine, medium and coarse grained rocks.
ü Abrasiveness: which is groped into non, slightly and very abrasive rock.
ü Tectonic properties: which are groped into very competent, competent, fairly
ü competent, fractured and highly fractured rocks.

5.How are these properties grouped?
ü •See the answers to question number 4 above.

6.What is the basic rule when choosing a suitable impregnated diamond drill bit?
ü In hard formations use a drill bit with a soft matrix and in soft formations use a drill bit with a hard matrix.
ü If we for example are drilling in a soft limestone, the diamonds can work during a comparatively long time before they are worn and it is then necessary that the matrix is hard in order not to erode too fast and thereby loosing the grip of the diamonds before they are worn.
ü If we on the other hand are drilling in a hard, fine grained, slightly abrasive volcanic rock the diamonds will wear out comparatively fast and it is then important that the matrix is soft enough to erode and expose new diamonds at the same pace as the old ones are worn.

7. Which are the most common impregnation depths (matrix heights) of an impregnated diamond bit?
ü 6 mm
ü 9 mm
ü 12 mm
ü 14mm
ü 16mm

8. What is the advantage of an extra high matrix height when drilling with wire line?
ü When drilling with wire-line systems a 16 mm matrix height is undeniably a great advantage. Compared to a 12 mm matrix drill bit, a 16 mm matrix drill bit will drill 20 – 40 more meters in a competent rock before it is worn and has to be exchanged. As everyone understands this mean less rod handling.

9.Which is the most common profile on an impregnated diamond core bit for wire line drilling?
ü The W-profile ( STD Profile )

10.Describe the difference between a front discharged drill bit and a drill bit with conventional waterways. Do also describe the formations that these two water way configurations are intended for.
ü When drilling in non-consolidated formations such as soil, sand, gravel, silt or clay there is a risk that the water will flush away part of the core.
ü A similar thing can happen when drilling in a fissured formation if the fissures are filled with a soft material. The water can flush away the soft material in the fissures and the rock mechanic has no way to tell whether the fissures where empty or filled.
ü For drilling under these circumstances front discharge flushing channels shall be used. In stead of passing in the annular space between the core and the inside diameter of the bit the flushing water will pass through channels inside the matrix and out via ports on the cutting surface. The contact between the flushing water and the very soft core is minimized and the risk for flushing away part of the core is much smaller.
ü Another advantage with front discharged drill bits is that the pressure drop over the ports is smaller than the pressure drop over the standard water slots. This will also contribute to a better core recovery in soft formations.

11. Which are the tasks for the reaming shell?
ü To ream the drill hole to the nominal diameter
ü To act as a stabilizer for the core barrel

1. What is the main function of the core barrel?
ü To store the core sample during diamond core drilling.

2. Which are the main components in a double tube conventional core barrel?
ü Diamond drill bit
ü Reaming shell
ü Landing Ring
ü Core lifter case
ü Core Lifter
ü Stop Ring
ü (Inner Tube Extension tube)
ü Inner tube
ü Outer tube
ü Core barrel head ( Head Assembly)
ü Inner Tube Stabilizer

3. How do you break the core? Describe the process.
ü When the inner tube is filled with the core sample the core barrel shall be taken up to the surface and the core sample shall be placed in a core box. The core sample is however a part of the rock and it has to be separated from the rock before the core barrel can be taken up to the surface. This operation is called to break the core. The core lifter case and the core spring are used to break the core.
ü These components are mounted on the inner tube. The core lifter case is tapered on the inside and the core spring, which is slotted, is tapered on the outside. When the core barrel is pulled out of the hole the core spring will grip the core and the harder the core barrel is pulled the firmer the core lifter will grip the core sample. When the pulling force is larger than the tensile strength of the rock the core will break. In a hard competent rock it might be necessary to use a pulling force of 10 – 20KN or more to break the core.

4. Why can’t the inner tube or the core barrel head take the loads that occur when breaking the core? How is this prevented?
ü Neither the inner tube nor the bearing assembly in the core barrel head are designed for the pulling forces necessary to break a hard rock core.
ü Therefore the core lifter case, the core spring and the inner tube can slide down and rest on a tapered shoulder inside the drill bit and thus the pulling force is transferred to the outer tube which is designed to take such forces.
ü The thin inner tube as well as the bearing assembly is thus completely without tension and/or loads during the core breaking operation.

5. Why should the inner tube not rotate and how is this prevented?
ü The function of the inner tube is to store the core sample during the drilling and the hoisting operations. It is important that the inner tube does not rotate since a rotating inner tube will destroy the quality of the core. The upper end of the inner tube is attached to a bearing assembly in the core barrel head. The bearing assembly includes radial as well as axial bearings which stabilize the inner tube and stops it from rotation with the outer tube.

6. Why should the gap between the core lifter case and the tapered shoulder inside the drill bit be adjusted from time to time? How is this adjustment done?
ü The flushing water passes first through channels in the stabilizer of the core barrel and then via the annular space between the core barrel head/inner tube and the outer tube and finally down to the gap between the core lifter case and the shoulder inside the drill bit. This gap can be adjusted by means of a nut on the core barrel head. When drilling in hard consolidated formation the gap can be fully opened enabling the flushing water to pass with as small pressure drop as possible. The part of the core sample located between the rock and the core lifter case will be flushed with water but as long as we are drilling in a hard and competent rock this does not matter.
ü On the other hand when drilling in soft and friable formation it is important to keep the gap as small as possible in order to guide the loose core into the core lifter case and in order to prevent that the loose core is flushed with water and possibly eroded.

7. Where in the core barrel is the water valve placed? What is the purpose of this valve?
ü Normally there is water shut off valve incorporated in the core barrel head. When the inner tube is filled with the core sample or in case of a core blockage, the inner tube is pushed against the core barrel head and the water shut off valve is closed.
ü This will block the waterways and the water pressure will increase. The driller will notice this, by looking at the water pressure gauge normally placed on the control panel of the drill rig, and he can then take the appropriate measures.

8. What is a triple tube core barrel?
ü A double core barrel can be equipped with a liner that is placed inside the standard inner tube. Thus the core barrel will consists of three tubes and is then called a triple tube core barrel. The liner tube is usually split axially and does thus consist of two halves. The reason for this is that it shall be easier to recover the soft core sample.

1.Describe the steps in wire line core drilling.
ü a. The drilling proceeds until core blockage or until the inner tube are filled with a core sample.
ü b. The overshot, which is attached to a wireline, is either lowered down the drill string or pumped into the drill string.
ü c. The overshot catches the inner tube assembly and releases it from the outer tube assembly.
ü d. The overshot and the inner tube assembly are hoisted up to the surface.
ü e. A new inner tube group is pumped down , or up, the drill string until it latches in the outer tube assembly.
ü f. The drilling starts new round again.

2. Which main components do a wire line core barrel consist of?
ü Outer tube group
ü Inner tube group
ü Overshot assembly

3.Which main components do the inner and outer tube assemblies of a wire line core barrel consist of?
ü The outer tube assembly includes the following parts:
Inner Tube Stabilizer
Locking coupling
Landing ring
Adapter Coupling
Outer tube
Reaming shell
Diamond Drill Bit
ü The inner tube assembly includes the following parts:
a. Head assembly
b. Inner tube
c. Landing shoulder
d. Stop ring
e. Core Lifter
f. Core lifter case

4.Which are the main differences between a core barrel head for a conventional core barrel and a core barrel head for a wire line core barrel?
ü On a conventional core barrel the inner and the outer tube is threaded to the core barrel head.
ü On a wire-line core barrel the inner tube is threaded to the core barrel head and this so called inner tube assembly is then held in place by a set of latches and the landing ring and shoulder.

5.What are the functions of the latches and the landing ring in a wire line core barrel?
ü The latches prevent the inner tube assembly from advancing up the drill string.
ü The landing ring prevents the inner tube assembly from penetration too far into the outer tube assembly.

6.Why is it important that the inner tube assembly has landed in the correct position before the drilling starts.
ü It is of outmost importance that the inner tube assembly actually has landed in the correct position before the drilling starts. If this, for some reason, is not the case and the drilling starts with the inner tube assembly in the wrong position this will be pushed into the drill string by the core sample.
ü The core sample will then be stored in the outer tube during drilling and the driller will probably loose the complete core from that particular core run.

7.How does the driller know that the inner tube assembly has landed in the correct position?
ü All wire line core barrels have some kind of a valve which should indicate that the inner tube assembly has landed. There are a number of different designs but two basic types can be identified. Both basic types of valves works on the principle that they block the water passage until the inner tube assembly has landed. When this happens the water pressure must reaches a preset value in order to open the valve and to give free passage for the flushing water.
ü An experienced driller does however have a number of ways to establish that the inner tube has landed in the correct position. He knows the time it takes for an inner tube assembly to travel down to the outer tube assembly. He listens for the specific sound that can be heard when the inner tube assembly lands in the correct position.

8.Which are the advantages and the disadvantages with a thin-kerf core barrel as compared to a standard core barrel?
ü A thin-kerf diamond drill bit contains fewer diamonds than a standard bit and
ü is therefore cheaper. A thin kerf bit does also require a lower feed force than a
ü standard bit and thus it has the possibility to drill a straighter hole.
ü A thin kerf bit produces a larger core sample than a corresponding standard core bit. A larger core sample is always an advantage for the geologists.
Ü A disadvantage with the tin kerf wire line core barrel is that it can not withstand
ü rough treatment and they are therefore not recommended for drilling in very broken formation.

1.Which types of drill rods are used in core drilling?
ü Aluminium alloy drill rods
ü Seamless Steel drill rods
ü Wire-line drill rods (welded pipes)

2.What are the purposes of the casing tubes?
ü To penetrate and stabilize the overburden
üTo stabilize non-stable formations with a tendency to cave in

3.Why should you always use full grip wrenches when working for example with inner tubes and core lifter cases?
ü It is important to use the right type of rod wrench. So called universal rod tongs should be avoided especially when it comes to breaking or tightening the thread of an inner tube or any other thin walled piping. Universal tongs can easily destroy thin walled piping. For these pipes only so called full grip wrenches should be used.

4. Which types of fishing tools should always be available on the drill site?
ü No matter how careful the driller and the helper are, sooner or later they will
ü accidently drop a tool down the drill hole. Drill pipes can also break in the hole.
ü These items must be removed before the drilling can continue. Normally, according to the hole size of the projects, we should prepare 1 or 2 sets of NWL(NQ), HWL(HQ), PWL(PQ) sizes of rod recovery rod at the site.

For wireline core drilling, the common sizes are B(55.6mm) N(69.9mm) H(88.9mm) and P(114.3mm)
The functions of the drill rods are:
Ø To transfer torque and rotation from the core drill to the drill bit.
Ø To transfer the lifting and pulling forces
Ø To serve a distribution line for the flushing water
Ø To serve as a distribution line for the inner tube assembly
There are drill rods for conventional drilling as well as drill rods for wire-line drilling.
Drill rods for conventional drilling can be manufactured from steel or from aluminium tubing but drill rods for wire-line drilling are always manufactured from steel tubing,we only select top quality 4130 raw material as the tubing to make the rods.
A wire-line drill rod has a male thread in one end and a female thread in the other end.
Right handed threads are commonly used. The threads are cut directly in the tubing and special separate drill rod couplings are not necessary. Thanks to this, so called flush jointed design, the wire-line drill rods have an even and a constant inner diameter which is a precondition for hoisting the inner tube assembly. The threads are surface treated or heat treated in order to prolong the life of the threads.
During the using of our rods, if there is any question, please do not hesitate to contact with our technical engineer for free.

Understanding the geology of worksites is paramount in exploration drilling. Below, a review of how the job is impacted by the prevailing rock conditions.

The geological conditions in open-pit mining have a direct effect on the efficiency and effectiveness of exploration work. From the most favorable conditions to the worst, the rock formations in the pit determine exploration drilling strategies, equipment requirements, and the quality of the samples that can be reasonably expected.

Productivity in core drilling depends on many different parameters, but the rock conditions is normally the biggest factor to affect the speed of drilling, and therefore the level of productivity as well the cost. Minerals and geology of the 118 known elements, some of which do not occur naturally, oxygen is by far the most common, making up about 50% of the Earth's crust by weight. Silicon forms about 25% and the other common elements such as aluminum, iron, calcium, sodium, potassium, magnesium and titanium make up 99% of the Earth's crust. Silicon, aluminum and oxygen occur in the most common minerals such as quartz, feldspar and mica. These form part of a large group of silicates that are compounds of silicic acid and other elements. Amphiboles and pyroxenes contain aluminum, potassium and iron.

Some of the planet's most common rocks, granite and gneiss, are composed of silicates. Oxygen also occurs commonly in combination with metallic elements, which are often important sources for mining purposes. These compounds can form part of oxidic ores, such as the iron ores magnetite and hematite.

Sulphur also readily combines with metallic elements to form sulphide ores, including galena, sphalerite, molybdenite and arsenopyrite. Chalcopyrite (CuFeS2) is also a very important and abundant ore forming mineral that contains copper. Other large mineral groups important in mining include halogenides such as fluorite and halite; carbonates such as calcite, dolomite and malachite; sulphates such as barite; tungstates such asscheelite; and phosphates such as apatite. Rarely, some elements can occur naturally, without combination. The important ones are the metals gold, silver and copper, plus carbon in the form of diamonds and graphite. Properties and characteristicsIt is true to say that mineralization is rarely pure. Instead, it is usually mixed, consisting of both homogenous and heterogeneous structures. Feldspar accounts for almost 50% of the mineral composition of the Earth's mineral composition, followed by pyroxene and amphibole minerals and then quartz and mica, making up about 90% of the Earth's crust.

In addition, minerals have a wide variety of properties and characteristics, and it is these that determine the best way to extract them.

Typical Characteristics Are:
• Hardness
• Density
• Color
• Streak
• Luster
• Fracture
• Cleavage
• Crystalline
form The particle size and the extent to which the mineral is hydrated (mixed with water) indicate the way the rock will behave when excavated (see geological methods, p.25).
Hardness is commonly graded according to the Mohs 10-point scale. The density of light-colored minerals is usually below 3. Exceptions are barite or heavy spar (barium sulphate – BaSO4 – density 4.5 g/cm3), scheelite (calcium tungstate – CaWO4 – density 6.0 g/cm3) and cerussite (lead carbonate – PbCO4 – density 6.5 g/cm3).

Dark-colored minerals with some iron and silicate have densities of between 3 and 4. Metallic ore minerals have densities over 4, and gold has a very high density of 19.3.
Minerals with tungsten, osmium and iridium are normally even denser. Although ore-forming mineral density may be high, the total ore density depends entirely on the host rock where these minerals exist.

Streak is the color of the mineral powder produced when a mineral is scratched or rubbed against unglazed white porcelain which may be different from the color of the mineral mass.

Fracture is the surface characteristic produced by breaking a piece of the mineral and is usually uneven in one direction or another. Cleavage denotes the properties of a crystal
which allows it to be split along flat surfaces. Both fracture and cleavage can be important to the structure of rocks containing substantial amounts of the minerals concerned.Rock is normally comprised of a mixture of materials. The rock may not only combine the properties of these minerals, but also exhibit properties resulting from the way in which the rocks were formed or subsequently altered by heat, pressure and other forces in the Earth's crust. It is comparatively rare to find a homogeneous rock mass, and the discontinuities such as faults filled with crushed material, major jointing and bedding non-conformities are hard to predict.

These discontinuities are also important, not only for the structural integrity of a mine and gaining access to mineral deposits, but also as paths for fluids that cause mineral concentrations in the Earth. In order for mining to be economically viable, the minerals have to be present in sufficient concentration to be worth extracting and within rock structures that can be excavated safely and economically. It must also be possible to enrich the minerals in an economical way. For mine development and production drilling, the rock must be correctly appraised because the results will affect projected drill penetration rates, hole quality and drill steel costs. In order to determine overall rock characteristics, it is necessary to distinguish between microscopic and macroscopic properties.

As rock is composed of grains of various minerals, its microscopic properties include:
• Mineral composition
• Grain size
• The form and distribution of the grain
• If the grains are loose or cemented together Collectively, these factors comprise the properties of the rock such as hardness, abrasiveness, compressive strength and density. In turn, these rock properties determine the penetration rate that can be achieved when drilling exploration holes and the extent of wear on the drilling equipment. In some circumstances, certain mineral characteristics will directly influence the mining method. Many salts, for example, are especially elastic and can absorb the shock from blasting. Good and bad conditions By far the best formation for drilling is hard, solid rock. The penetration rate is higher, the wear on consumables low, and the hole deviation less. Conversely, if the formation is softer and has cracks and layers, hole deviation increases, consumables wear quicker, penetration rates are lower and the risk of getting stuck, or losing parts of the core, is higher. It may also be more difficult to keep the hole open and prevent it from collapsing. Flushing the hole is also extremely important and can make the difference between success or failure when drilling. One common problem is water loss. This occurs when drilling is carried out in bad rock formations with a lot of cracks through which much of the water can drain away. The greater the cracks, the more water will be lost. In more fragmented rock conditions, the water can often be lost completely which has an extremely adverse effect on the drilling process, damaging equipment and jamming drill rods in the hole. The technique of water flushing differs greatly depending on the rock formation. In hard rock conditions the possibility to use water alone is higher, while in soft rock formations there is often a need to use polymers or mud. Flushing is done for several reasons. It cools the bit,cleans the face in front of the bit and bring the chips to the surface, reduces the friction between the rod and the hole and reduces vibrations in the drill string.

Hole flushing in unstable formations is far more complicated than in hard formations since it is necessary to keep track of the density and viscosity of the fluid used to flush the hole. It is also required that the driller understands the relationship between these parameters and the stability in the hole, the capability of the fluid to transport sand and chips to the surface, the ability to control loss of water and the ability to build up a filter cake in the hole. Flushing in these adverse conditions is also used for other reasons, too, such as stabilizing the hole, sealing cracks and increasing the capacity to bring the cuttings to the surface.

The driller’s challenge Today, exploration drillers face a range of different challenges, not least that geologists are demanding bigger and bigger core samples. The bigger the sample, the more information can be obtained. This presupposes, of course, that there are drill rigs that can handle these large size cores at the specified depths.

The depths required are also getting deeper due to the fact that the shallower deposits are already being extracted. Furthermore, adverse rock formations make the driller’s job trickier since it is then more difficult to extract core samples that are of good quality and intact at an acceptable cost. Today’s exploration drill rigs go a long way to meet these demands and increase productivity at the same time, thereby enabling the exploration driller to increase earnings. One major benefit is that these rigs provide more detailed information on the various parameters which enables the driller to monitor the events more closely while drilling and to take any necessary action before something goes wrong. In addition, innovation with regard to In-The-Hole (ITH)technique is also making life easier by helping the driller to ensure that the overshot is properly connected when retrieving the core. This reduces the need for maintenance on the ITH equipment and improved of the diamond bits. If it is possible to improve the performance of the diamond bits, the same bit will last longer. This means that the intervals between bit changes become longer and productivity increases. Changing the bit is time consuming. The deeper the hole, the more time is spent tripping rods in and out of it. The vision of automation There is no doubt that most companies developing core drilling equipment are heavily focused on increasing the level of automation in exploration. Initially, this may only be limited, for example to enable a rig to drill one rod automatically during a shift change. But it is clear that the aim is to automate more, eventually to enable a whole round trip to be completed automatically.

However, to be able to run a core drilling rig fully autonomously is a very long-term vision. Core drilling rigs are muchmore complex than those designed for drill-and-blast. Arguably, the development of core drilling equipment is more focused on extracting detailed data from the rig that can enable the driller to analyze exactly what is happening during the drilling process. In addition to this, developers are also focused on increasing the amount of data that can be extracted from each rig, so that the differences between different drillers and rock formations can be studied. Other innovations under development include the transfer of data to remote sites to inform drillers of when it is time for maintenance, and when an event may potentially lead to a breakdown.

If there is any question for how to improving the drilling efficiency, and how to choose a right impregnated diamond bits, reaming shells, and related drill rods, contact with our technical consultant by free. WhatsApp: +86-188 5151 3960

Diamond Core Bits used for exploration drilling are almost always mounted with diamonds.
A diamond is the hardest known naturally occurring mineral. In fact it is the hardest material that we all know. Diamonds can thus cut in almost any other material from earth.

Diamonds do also have another quality which makes them suitable for use in core bits.
They do have a very high coefficient of thermal conductivity.

When the diamonds cut the rock a large amount of friction heat is produced. Thanks to the very good thermal conductivity of the diamonds this friction heat can be removed by means of the flushing fluid.

TC Bit is also a way, but it does not have the same good thermal conductivity and thus it can only be used for drilling in soil and other very soft formation which does not create anywhere near the amount of friction heat created when drilling hard formations.

There are two types of diamond core bits i.e. surface set diamond core bit and impregnated diamond core bits. Only natural diamonds are used for surface set bits. With natural diamonds we mean diamonds that are mined. For impregnated core bits only synthetic diamonds are used. With artificial diamonds we mean man-made synthetic diamonds.


The technique for manufacturing synthetic diamonds has had a fast development during the last decades. Today the synthetic diamonds are superior to the natural diamonds both in terms of life length and cutting ability.30 Another advantage with the synthetic diamonds is that these can be give special qualities required for core drilling. The synthetic diamonds can thus be “tailor made” to suit drill bits intended for different types of rock. Brittleness, grain size and geometry are three important characteristics that can be “tailor made”.

Diamonds are a form of carbon. Unlike graphite, which also is a form of carbon, they are very hard and this is due to the strong bonds between the carbon atoms. Diamonds have a thermal stability up to around 800 degrees Celsius. At higher temperatures a gradually graphitization will take place provided that air is present.

A diamond drill bit consists of diamonds, a matrix and a steel body. The matrix is a metal powder i.e. a mixture of different metals grains. The composition of the metals is depending on which physical properties the matrix should have i.e. soft, hard, wear resistance, ……..

When manufacturing impregnated diamond core bits the diamonds and the matrix are mixed together. The mixture is poured in a graphite mould and pressed together. The graphite mould, together with the steel body and a bond, are placed in a furnace and is heated to high temperatures. The bond will solder the mixture of the diamonds and the matrix to the steel body.
In order to prevent graphitization of the diamonds the heating takes place in a controlled atmosphere.

During this metallurgical process the metals in the matrix are sintered and infiltrated to a homogeneous structure with a very high wear resistance.

When manufacturing surface set diamond core bits natural diamonds are set on the inner envelope surface of a graphite mould which then is filled with a matrix. The graphite mould together with the steel body are then placed in the furnace and are heated in the same way as the impregnated diamond core bit.

A surface set diamond bit cuts the rock whereas an impregnated diamond bits works on the rock by means of a grinding or a wearing action. The axial motion of the diamond bit, which is called the penetration speed, is depending on several factors. Some of these factors can be controlled by the driller while others can not.
The driller can for example control the flushing, the choice of drill bit and the drilling parameters but he has no control over the geology, the hole diameter and the hole depth.One of the most important keys to successful and productive core drilling is to create a balance between the factors that the driller does have an influence on. We will look closer into this in the chapter Drilling Technique.
Welcome anyone to share us with your idea for diamond core drilling.

The diamond core bit we can provide:
NQ diamond core bit
HWL core bit impregnated
PQ imp diamond bit
HW casing shoe diamond
HWT diamond case shoe bit..

Contact with our technical person for getting further supports for diamond core drilling.
WhatsApp: 0086-18921310502

Stand-Off Gap Excessive or Does Not Close Upon Minimal Make-Up or Difficulty Breaking Out
* Clean and inspect threads for excessive foreign or wear debris.
* Accelerated wear may be due to damaged accessories - inspect accessories (e.g. adapter subs).
* Rods of different manufactur are to be separate and do not interchange these rods.
* Threads are deformed from overload or excessive load during make and break. Inspect string for damage and discard rods with deformed threads. Overload or difficult breaking may be due to poor choice of thread compound (see lubrication and cleaning and break-out).
* Deformation due to hammering damage (see break-out) or stabbing damage (see stabbing).
* Inspect string and discard damaged rods.

Fatigue Failures or Cracked Pins or Boxes (See Fatigue Strength)
* Extraneous hoop stresses (see glossary) caused by deformation due to hammering damage (see break-out), stabbing damage (see stabbing), excessive foreign debris, or wear debris in the joint (see thread wear).
* Box shoulder deformed due to overload leaving pin or box unsupported. Overload may be due to poor choice of thread compound(see lubrication and cleaning). Consider upgrade to AU rods.
* Bend stresses have exceeded the fatigue strength of the joint. Bend stresses are caused by excessive steering, excessive hole deviations or caves, or helical whirling (see midbody wear). Do not exceed deviation ratings. This may have been compounded by high pullback loads at depth or excessive make-up. Plan deviations to occur at portions of the string that are under low pullback(e.g. avoid the upper portion of a deep hole string).Fatigue strength may have been exceeded in previous application and joint has now reached limit (see memory and fatigue strength).
* Rods run in loose (joints not closed) due to insufficient make-up or to excessive stand-off gap (see causes of excessive stand-off).
* Box wear life exceeded. Inspect string for excessive wear (see wear life).
* Rods string has suffered from hydrogen embrittlement (see glossary). Replace rod string and use non-metallic thread compound.
* Rods are of different manufacture. Separate all rods by manufacturer and do not interchange.

Leakage (See Fluid Seal)
* Box bulging due to excessive hoop stresses (see glossary) imposed by thread, potentially from overload.
* Evident by polished areas on one side of box or thread jumping in the extreme case. Overload may be caused by poor choice of thread compound(see lubrication).
* Box wear life exceeded leading to overload.Inspect string for excessive wear.

Thread Wear or Galling (See Thread Wear)
* Thread compound has failed to prevent mating thread surfaces from interacting. This is due to either a poor or diluted compound or poor lubrication practice. Upgrade thread compound or increase frequency of cleaning and re-lubing joints.
* Thread contact pressure is excessive. For stab flank wear, reduce feed rate/pressure and/or increase rotation during make and break.
* For load flank wear, increase feed rate and/or reduce rotation during make and break. Rods with significant load flank wear should be discarded.
* Accelerated wear may be due to damaged accessories; inspect accessories for damage or wear (e.g. adapter subs).
* Thread wear life exceeded. Accelerated wear may be due to damaged accessories; inspect accessories (e.g. adapter subs). Inspect string for excessive wear.

External Shoulder Wear or External Shoulder Flared/Rolled Over
* Box shoulder flared and/or pin outer shoulder rolled over due to overload.
* Overload may be due to poor choice of thread compound (see lubrication).
* Box shoulder wear life exceeded. Inspect string for excessive wear.

Box Wear or Box Bulging or Thread Jumping (See Box and Midbody Wear)
* Box bulging due to excessive hoop stresses (see glossary) imposed by thread, potentially from overload.
* Evident by polished areas on one side of box or thread jumping in the extreme case. Overload may be caused by poor choice of thread compound(see lubrication).
* Box wear life exceeded leading to overload.Inspect string for excessive wear.

Premature Midbody Wear or High Drilling to Que
* Hole deviations (e.g. rotary drilled holes, wedging, or down-hole monitoring) induce increased contact pressure and friction between string and hole or casing wall.Improve lubrication of string to compensate.
* Hole has oversized or ‘cave’ sections allowing the string to elastically bend or buckle under load increasing contact pressure and friction.
* Reduce drilling loads or rotation speed to compensate or repair hole.
* High pullback or thrust load combined with high rotation speed has caused the string to elastically or permanently bend, increasing contact pressure and friction against the hole or casing wall.
* Evident by polished or heavy wear on one side of string in a slow spiral pattern (e.g. spiral has a multiple length pitch). Reduce drilling loads and/ or pullback.

Geo Equip Tech Wuxi (CGEGTECH) as a professional supplier in China for diamond bits and reaming shells, we would like to share some of our experience to our global customers.

All we know the correct selection of impregnated diamond bit is very important to driller and distributor. Normally there are 4 sizes of diamond coring bits in the market for wire-line core drilling, they are B, N, H and P sizes, for making sure the bits can work with the rock formation properly, we need to do a selection before an order according to the ground conditions and bits selection chart from the manufacturer. So is there any skill for select a proper drill bit?

There are some skills according to our experiences, we would like to share with you as per following:
Skill I Rock Property ( Hardness) Firstly we need to know the something about the rock properties, for example, what is the rock, how about the rock hardness, the drillers in our industry like to use Mosh Scale to identify the hardness of the rock, secondly, how about the rock abrasiveness, the rock grains are fine or coarse, all of those factors will determine how difficult of drilling and the penetration speed.
Skill II Bit Selection Chart Normally, all of the manufacturer will have a impregnated diamond bit selection chart, it shows their diamond bits characters, and how their bits work with various hardness of the rock, as a practice, most of the experts in our industry will clarify the ground as 3 parts, Soft to Medium Hard, Medium Hard to Hard, Hard to Ultra Hard, so you can choose the right bit very easy.
Skill III Drilling Rigs Different kinds of drilling rigs, their feeding power and rotation speed are different as well, those will also have the influence of our selections. Usually, the hydraulic drilling rig has the most powerful feeding strength and rotation speed if compare to portable drilling rig and conventional spindle drilling rigs. For example If you are using the LF-90D drilling rig, it is hydraulic and very powerful, for an instance, for Mosh Scale 7-7.5, we suggest you to use RH10 at first, if after the using, it can’t meet your penetration speed requirement, then try RH12, however if you had a spindle drilling rig at the work site, and you plan to use it, for the same rock formation, we suggest you to try RH 12 at first.
Skill IV Rock formations Apart from the hardness of the bits, broken or competent is the another important factor for how to select a correct bit, if the rock is broken, you can try our lower bit # ( For Example: RH12), if the the rock is competent, try higher bit # ( For Example: RH14).
Except the above skills, also the penetration speed and service life of the bits will affect the selection of the bits, contact our sales engineer to get free technical consultations today!

Geo Equip Tech Wuxi ( CGEGTECH ), integrates R & D, design, production, sales and technical services. Relying on the unique advantages of high-quality raw material selection, the company takes the production of high-quality diamond bits and drilling tools as its own responsibility, serves the drilling field as its purpose, takes the lean production mode as the guidance, promotes the continuous improvement of products with rigorous management measures, and strives to provide customers with products that can be used safely.

Keywords:
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* How to select a bit

Impregnated diamond core bits must maintain good diamond exposure in order to drill into the rock efficiently. Sharpen the bits before normal using is very important, there also some another factors work in unison to provide the controlled erosion cycle of the bit's segments. When this controlled erosion cycle is altered, the bit can become dull or glazed. Glazing becomes noticeable when the coring feed rate slows dramatically or the bit does not cut. Examine the bit immediately. If the diamonds are flush with the metal, they are underexposed or glazed.

The following steps will often correct this problem:
1.Reduce water flow until it becomes very muddy. Continue using as little water as possible until penetration increases.
2.If bit does not open up, remove from hole. Pour into kerf a thick (1/4") layer of silica sand, the coarser the better.
3.Resume coring for approximately 3 to 5 minutes with very little water and at a lower RPM if possible.
4.Gradually increase water flow to flush sand from kerf.
5.Repeat as needed.

Contact with our technical guys to know more
WhatsApp:189-2131-0502

The correct selection of impregnated diamond bit is very important, it will determine how the performance going, and how long the bit working in the hole. Good material and high technology process just are the beginning of making qualified IMP bits, also there are some requirements for users. The user or distributor must have some specific knowledge of Geological Drilling and Diamond Core Drilling Methods, also they should learn the characters of the rocks, different hardness of the rock request different cutting force and the penetration ratio is different as well, only the bit matches the rock, it can make good progress in drilling, of course the diamond core drilling is a little complicated to most of the drillers if they want to make good performance drilling, the drilling rig plays important role in drilling, too. Here we highly recommend to use hydraulic drilling rig, it has higher RPM and stronger torque than mechanical drilling rig, when the diamond bit is working, the diamond will be exposed and be sharped to cut the rocks, it need high RPM and higher torque to force the diamond layer exposed easier to cut the rock, through this way which can make fast drilling( At the very beginning of drilling, we need to sharp the bit with relative low RMP and less torque)

4 days ago, our customer Mr Ersoy’s company used Boart Longyear LF90D plus our Master grade of RH4, RH6 and RH8 impregnated diamond bits made very good performance at their working site in Turkey, before that their first choice are Hayden H4, H6 and KS5 series of bits. Mr Ersoy is a very professional drilling supervisor, we talk a lot details of their project before placing order, after the discussion, he thinks RH4, RH6 and RH8 can meet their requirements. According to the feedback from him, the rock over there are andesite, kalkshist and quartz, mosh scale changed from 4 to 7.5, some of them are soft and broken, some of them is broken and hard, finally the average working life for the above bits are 241.5m, RH8 lasted for 261.0 m, also we got the news that our HWL natural diamond reaming shell heavy duty type can last over 1500m, excellent!

Let me share some technical information of their drilling at worksite

As we know the waterways design is a very important procedure before impregnated diamond drill bits making. Let’s take HQ impregnated diamond drill bit as an example:

Abrasive is one of the characters for some of the rocks, however for diamond coring drilling, this is a problematic thing to most of the drillers in the world. It probably will be difficult to drill through for any hardness of abrasive rocks, and it will cause premature wear out of the diamond bit, especially for the hard abrasive rock formation.

Fortunately, now perhaps you can try our RH8、RH10 Bit as a good option for those boring ground conditions, these lines of bits are developed specially for such conditions, the bits has wider waterways, which can make sure the water flushing out cuttings easier, and cool the bit efficiently.

RH8 and RH10 is available for NQ, NQ3, HQ, HQ3, PQ and PQ3 models.

Have a try，and have a talk with our sales engineer for getting more technical support.

All of the drill rods and casing products are made according to the strict quality control standard from APR Tools, here we have the most advanced production facilities in China, Mazak Smart CNC, imported heat treatment equipment from USA, high machining accuracy of both ends of threads, they can provide a tight mechanical seal for getting better performance, with the good care with thread grease, our rods never leaking even if working in very harsh conditions, we only choose premium quality of AS4130 raw material to make the rods and casing, it has impressive good of straightness, which can keep the rod string in the hole is very straight, so it can reduce the risk of hole deviation. Helping our customers to get faster penetration rate, recommend to use our Master grade and Victor grade of bits as a good partner to keep super penetration speed.

Note:C80 material is an option for casing.

Need free technical supports? Contact with us today!

PDAC event is one of the world’s premier mineral exploration & mining convention. Here we can find the trends for the global mining industry, every year, lots of world famous mining companies, associations and manufacturers will take part into this big event.

However, since the pandemic, PDAC 2021 is holding as a video link conference. Hope to see our customers and friends soon next year.

We will definitely bring our latest product samples for a show. Such as Impregnated diamond bit, reaming shells, drill rod subs, adapter couplings, locking couplings, head assembly and overshot, all of those can help our customers know more details about our company. To understand our product information, please visit our website: www.cgegtech.com

Share with your wonderful story for diamond and RC drilling to our blog, contact with Mr Kor +86-18921310502 for starting a conversation.