The most common practice, in this case, is to drive T45 or T38 rods for percussive drilling and API rods for rotary drilling. But when the customer was drilling with top hammers, his drillers had to change the complete tooling setup from API rods to percussive rods and vice versa. This proved to be ineffective and was burning resources on job sites and in tooling stock. The customer came to Boart Longyear for a rod solution that would be able to drill both rotary and percussive without changing the tooling set up.

Our engineers designed the new CBXP rods capable of both rotary and roto-percussive. By using the new rods, the customer reduced his spend on drill rods by 60% annually, purchasing one dual-purpose CBXP rod, instead of having to buy twice the number of rods for the two types of drilling. Productivity on job sites increased as changing tooling between the two different drilling applications was unnecessary.

CBXP drill rods are designed to be used as inner drill strings in double-head drilling applications. CBXP rods offer a more robust design than the common API rod and outperform API rods in durability and performance, especially when occasional percussive drilling is involved. It combines the effectiveness of an API rod but comes with more advantages than T38 and API rods, like:

• Higher flushing for higher penetration compared to API
• Longer thread life with an asymmetric thread profile
• Can be used for roto-percussive drilling (e.g. drilling though overburden boulders)
• Higher outside diameter compared to T38 & T45 rods results in higher flushing speed
• Conical thread shape provides better alignment for quick and easy make and brake
• Dual drilling capabilities as it can be used in both rotary and percussive applications

CBXP drill rods are primarily intended for use in rotary and rotary DTH drilling applications but are also commonly used as the inner drill string on double head rotary-rotary applications or in a single head rotary duplex application. CBXP may also be used for smaller percussive drilling applications. The rod ends of our CBXP rods are constructed of high tensile strength quench and tempered steel and are gas nitrided to provide additional life. Rod ends are friction welded onto mid-grade mid-body material. CBXP rods are manufactured in a variety of lengths and wall thickness. Boart Longyear can manufacture alternative rod lengths and spanner flats upon request.

Boart Longyear began manufacturing overburden and construction drilling products in 1989 at its facility in Germany to serve the foundation construction market. Boart Longyear overburden and construction tools were quickly recognized by the industry as reliable and well-designed. From the start, customers appreciated the use of high-quality steels, precise heat treating and thread gauging as well as the development of new tungsten carbides for the drill bit line. The attention to detail with the overburden and construction drilling tooling product line has made Boart Longyear one of the most respected names in the industry.

Today, Boart Longyear manufactures a broad offering of overburden and construction tooling at our 5000 m2 (54,000 ft2) facility in Eiterfeld, Germany. The modern ISO9001-certified facility hosts an array of advanced manufacturing capabilities including CNC (computer numerical control) machining, friction-welding, and induction hardening equipment for rod and casing products, as well as computer controlled ovens for assembly of tungsten carbide-tipped bits and tools.

Check out the full-line of Boart Longyear overburden and construction tooling by downloading the catalog.

When purchasing top hammer button bits, for example, choosing a high-quality product designed for the specific ground conditions is only the first step to achieving more meters per bit. Ensuring bits are properly used and maintained is critical to realizing a high return on investment.

When a top hammer button bit is sharp, the percussive energy transferred into the rock is at its optimum, resulting in effective rock fracture and a maximum penetration rate for the given drilling parameters.

As flats develop on the buttons (tungsten carbide inserts), energy utilization is no longer optimized, leading to a lower penetration rate and reduced productivity. As buttons wear, the bit is less effective at fracturing the rock and the energy is dispersed over a larger surface area. Instead, rock is ground, rather than cut, producing smaller cuttings and energy (no longer used for breaking virgin rock) is reflected back up the drill string. This reflective energy contributes to increased loads on the tooling, drifter, and rig. As a general guideline, refurbishing the buttons before the flats reach 1/3 of the button diameter will maintain penetration/productivity, provide maximum bit utilization and help extend the life of all drill string components.

If the button flats are allowed to develop further to where they are considered over-drilled, productivity and the rate of penetration deteriorates. In this situation, much of the rock in contact with the buttons is re-drilled and the steel bit face may make contact with the bottom of the hole. Fewer and smaller rock chips are produced and much of the energy is reflected back up the drill string. This sacrifices the life of all the drill string components is a major contributor to hole deviation, increases wear and tear on drill rig components and results in higher operational costs overall. Top hammer button bits that are over-drilled exhibit broken buttons and impact drilling productivity.

Button bit wear patterns vary depending on the type of ground and the drilling parameters:

If drilling through hard materials such as sandstone and quartzite, drilling with excessive rotation, the wear tends to be greater on the bit circumference. Thus, when the buttons are sharpened, the diameter across the gauge is less than or equal to the diameter of the bit body. In this situation, the bit tends to bind (gauge-out) in the hole. Drillers should consider bit replacement or restoring the gauge button-to-body gap to the original (new) condition.

Harder ground conditions and drilling with excessive rotation creates wear that tends to be greater on the bit circumference.

When drilling in non-abrasive materials, carbide wear is minimized and drilling intervals are possibly longer. This allows for continued chip removal around the bit and wears away the bit body quicker than the carbides also referred to as body wash. Similar wear occurs in fractured and loose formations where constant hole cleaning and re-drilling of the materials is required for stabilizing the hole and to keep the hole open during retraction. To prevent button loss or shearing under these conditions, the protrusion should be reduced to the original height by scheduling grinding intervals.

Body wash often occurs when drilling in non-abrasive materials.

The detrimental effects of over drilling button bits may not be immediately apparent. However, running dull bits not only slows down drilling rates but escalates costs by reducing the life of the drill string components, the rock drill and the rig components. Premature button bit insert failures are substantially reduced when over drilling is eliminated and correct sharpening procedures are performed.

Premature button bit insert failures are substantially reduced when over drilling is eliminated and correct sharpening procedures are performed.

To get the most out of top hammer button bits, training drillers and mining management on bit care, maintenance and identifying excessive wear can increase the return on investment.

Understanding the ground conditions and regular inspections of a button bit are necessary to prevent over drilling. To ensure optimal performance and life, bits require sharpening before the flat exceeds 1/3 of the button diameter. Working with a technical representative is recommended to establish specific guidelines since the maximum suggested wear before reshaping will depend on the button profile.

Drilling in non-abrasive ground can give rise to ‘snakeskin’ (small cracks) on the button surface. If it is not removed by grinding, button fatigue failure occurs.

Drilling in non-abrasive rock results in the bit face wearing faster than the inserts. Excessive insert protrusion, lacking sufficient steel support, can easily break while drilling and when retracting the bit from the hole. To prevent this from occurring, grind the buttons to restore the protrusion height.

If button protrusion is adequate, satisfactory re-sharpening can be achieved by use of a preformed diamond faced tool (‘cups’). Sharpening is performed by holding the tool firmly against the button and orbiting the machine in a circle to achieve a uniform surface finish. Diamond faced tools are designed to cut carbide and not steel. It is therefore recommended to have enough protrusion of the button from the face to avoid damage to the cup, bit or grinding machine.

It is important to implement effective grinding tool management since the tool profile gradually changes leading to buttons that no longer match the desired shape. Technical representatives can assist by providing specific recommendations.

It is always important to care for and maintain tooling and equipment. Consider a “bit” of training for drillers on getting the most life out of the top hammer button bits. More often than not, drillers come to work to do their very best and everyone wants to improve. Provide them with an opportunity to better their drilling habits by sharing these tips.

From a complete selection of rods, bits, and shanks to couplings, adapters, and other accessories, Boart Longyear provides top hammer tooling solutions for any percussive drill and blast application for both surface and underground drilling.

For more information on Boart Longyear top hammer tooling, visit our webpage or download the catalog.

SAFETY ALERT: Use appropriate eye protection, masks and ventilation when grinding drilling bits. Grinding wheels and tungsten carbide inserts contain: Tungsten Carbide; Cobalt; Tantalum; Chromium; Nickel; Aluminum and Silicon. Grinding tungsten carbide inserts releases particles containing these elements that can irritate skin, eye, nose, and throat and can result in lung damage.

Boart Longyear historically named their overburden and construction drilling products line for this type of drilling “Delta” tools. In addition to being the fourth letter of the Greek alphabet, and a code word representing the letter D, (used in radio communication), delta is also defined as the difference between two things or values, or the average change of any changeable quantity. In short, the overburden construction drilling product line was designed for drilling through changing ground conditions typically encountered above bedrock.

With more and more challenging and larger specialty geotechnical construction projects in difficult, complex, and varying ground conditions, rotary and percussive drill rigs in the construction industry were getting stronger and more powerful. Bigger, stronger, and more powerful rigs subsequently required larger, stronger, longer-lasting construction drilling tools – including better designed and manufactured casing bits.

Casing bits are used in deep, difficult overburden when a casing shoe is not sufficient to drill to depth. There have not been any significant advancements made in casing bit designs since the 1990’s. The so called “proven, bullet-proof” bits were made day after day without questioning the physical mechanics or what might be possible with a new or improved design.

In light of this, Boart Longyear decided to partner with its customers to look at redesigning casing bits in the geotechnical construction drilling field.

The first discovery in this initiative was that drilling site feedback often compared apples to oranges about bit designs and there was no real definition of drilling bit designs or any so-called standard. The sum of differing opinions needed more segmentation and analysis. After interviewing customers, experienced drillers, and engaging our internal engineers, all of the feedback was segmented and combined with proven manufacturing information and our new Z Design casing bits were created, tested, and are now available to the industry.

Combining the three main aspects in faster and longer lasting casing bits: cutting, flushing, and gauge protection, Z Design casing bits provide improved flushing, faster ROP (rate of penetration), and longer lasting bits. The difference is in the design and materials. Using premium tungsten carbides, high quality steel, improved gauge protection, and induction brazing to reduce blistering, Z Design casing bits are manufactured in our ISO-Certified, Eiterfeld, Germany manufacturing plant.

CONSTRUCTION

Casing bit bodies are constructed of high strength quenched and tempered steel. The high-quality tungsten carbide inserts are induction brazed into the steel bodies ensuring a secure fit without overheating issues associated with flame brazing. Strict machining control of the carbide seats prevents premature loss of carbide inserts.

GAUGE PROTECTION

Tungsten carbide gauge protection on casing bits prevents excessive wear on the outer diameter of the bit in abrasive ground conditions. Additionally, in unconsolidated conditions where the ground is caving in on the drill string, gauge protection assists in freeing the bit and casing by providing another cutting surface.

SHRINK FIT CARBIDES

When required, Boart Longyear offers shrink fit installation of all hemispherical, ballistic, and two-step tungsten carbide inserts instead of the standard induction brazing. This very precise construction method is often utilized when drilling in extremely hard ground conditions and provides both increased button retention and longer overall life.

ADVANTAGES

• Computer controlled induction brazing of tungsten carbide inserts for superior process control and overheating prevention, common with flame brazing
• High-grade body construction with quenched and tempered steels
• Optional tungsten carbide gauge protection available for unconsolidated grounds and increased bit life in abrasive conditions
• Specialized designs for unique drilling situations such as drilling through reinforced concrete and drilling without inner bits.

Better casing bits means better drilling outcomes and ultimately results in better ROI (return on investment). Casing bits are designed for rotary percussive or rotation only drilling based on the tungsten carbide inserts utilized as well as the geometry of the bit. Customized tools for unique drilling applications are also available upon request.

Contact your local Boart Longyear representative or distributor to order the best casing bits in the overburden drilling market. Still not convinced? Contact us for help designing and implementing a testing drilling program to prove using Boart Longyear casing bits have a higher ROI.

For part numbers, download the Boart Longyear Overburden and Construction Tooling catalog here.

With the current procedure, the StopeMaster rig had to be escorted by a scoop in front of and behind the equipment on every move. The StopeMaster rig is essential in production drilling in the mine, but slow to move and it would hold up traffic on the ramp as it moved throughout the mine. This process was costing the mine time and resources.

In order to solve this challenge, Boart Longyear’s Drilling Services engineering team created a multi-phase plan to add both functionality and mobility to the existing StopeMaster equipment. The first phase of the plan was to design and build a more mobile StopeMaster rig, then move to hands-free rod handling, and finally to semi-autonomous drilling.

With the combined dedication of many remarkable Boart Longyear employees around the world, the team started engineering a new Stopemaster MDR rig that would solve the issues the mining company was experiencing.

A few weeks before the MDR rig was to be delivered, representatives from Boart Longyear’s Drilling Services team accompanied the mine’s pre-assessment team to scour every nook and cranny of the prototype rig to proactively identify and address conformance to the customer’s standards.

To ensure successful deployment of the new StopeMaster MDR mobile drill rig, a specialized Boart Longyear team spent 16 days onsite working out all the fine details and making sure everything was up and operating smoothly. The team included dedicated percussive drillers and a senior production designer.

On the afternoon of March 10, 2018, the very first Stopemaster MDR rig took to the ramp as it entered the portal for its inaugural deployment at a mine in Northern Ontario, Canada. Shortly thereafter, it collared its very first hole.

From the moment the rig arrived at the mine, the Boart Longyear team worked diligently with the customer to rapidly address any new concerns identified by the onsite reviewers. Over the subsequent days, the drilling team quickly learned the new LMi interfaces - a couple of joysticks, a knob, and a touchscreen had replaced the recognizable matrix of gauges and controls native to the stalwart StopeMaster machine. 

(Left-to-Right) Boart Longyear employees: Willie Coderre, Tyler Allin, Zane Clark, Al Portugie, James Forest, Dan Kirkey

After days of fine tuning the rig and tweaking the software controlling the rod handling aspects of the drill, the drillers were finally allowed to drill. These enthusiastic men cooperated as a tag team to complete the first 17-meter hole that expectantly broke through a known water fault that cascaded 4°C water down onto the drill and drillers. 

Then it was time for a crew change, and a new set of drillers embarked on the project. The next hole had to be drilled in the stope with a cascade of refreshing Canadian ground-water endlessly spewing onto the drill. Without much of a grumble, the assigned driller donned his oilers and dutifully braved the damp, frigid conditions, rod after rod. The drill was struggling to dig with the last few rods, so the dedicated driller pulled them all to check the bit, then sent the drill string right back up. Only later was the penetration issue attributed to a malfunctioning valve, but the driller trudged through. With half a meter to go, the shift was over and it was time to quit for the day.

Due to logistical challenges that followed, some members of the drilling crew were, for one reason or another, temporarily unavailable. Another team member accepted the challenge of training on the new drill.

Willie Coderre tramming the MDR into its first Stope.

He diligently battled through the still undiagnosed valve issue to complete the last half meter of the previous hole and followed that performance up by completing a 17-meter-long hole of his own. With the drill onsite for well over a week at this point, the latest driller now held the “Most Meters Drilled” title for the new StopeMaster MDR rig. 

After agonizing over the extremely slow penetration rate, the striking bar on the drifter snapped with only three more meters left in the hole. The crew replaced the striking bar and completed the stubborn hole. 

While repositioning the drill for the next hole, the driller was quickly able to identify a weakness in one of the actuators that deploys the drill’s outriggers. The drill was again shut down and made safe before the team made their way back up to the surface to brainstorm a plan to reinforce the outrigger. With a plan in hand, the team took another maintenance day to execute the fix.

With the outrigger issues now resolved, the drill was successfully repositioned and began another hole, this time with the team focusing a keen eye on the detailed micro-behaviors throughout the drilling process. The drilling team was able to identify and diagnose the misbehaving valve and in no time, the new drill received a replacement part. A couple of hoses here, a few bolts there, and the feed pressure control was snatched from the Programmable Logic Controller (PLC) and temporarily placed back into the hands of an experienced longhole driller.

Finally, with multiple issues resolved, the team united to attempt to get some meters drilled without issues. With the drill behaving much better, five holes were easily drilled for a total of 83 meters that day.

Although challenges were initially experienced with the prototype, having the Boart Longyear team available onsite meant they could quickly adapt, adjust and correct any problems. Because of their dedicated teamwork, the crew was able to deliver on the customer’s request to upgrade the StopeMaster to a mobile drill rig with rod handling and semi-autonomous drilling.

The newly commissioned StopeMaster MDR rig solved the issues of moving the StopeMaster, making moves from stope to stope faster and requiring less time and resources from the mine. The StopeMaster MDR equipment is also safer with rod handling capabilities and semi-autonomous drilling with a new LMi control panel which controls both the rod handler and the StopeMaster MDR rig.

Once the right tools for the job have been determined, attention must be paid to their condition and performance. The nature of top hammer operations in extreme environments means that wear will quickly have an impact on how long various components can be used before replacement is required.

These tools represent a relatively small operational expense; however, incorrect use of the tooling can have a significant adverse impact to overall costs.

In regards to wear, bit condition will have the most immediate impact on drilling success. Drilling with worn bits not only decreases productivity but also escalates costs by reducing the life of the drill string components, the rock drill, and the rig components. Over time, direct contact with the rock and the extreme energy being applied to the tooling takes its toll on the bit and its buttons, making their condition deteriorate.

There are many factors that contribute to premature bit wear, whether it’s ground conditions, risky drilling practices like hole collaring, excessive feed pressures, or not maintaining equipment correctly. Premature bit failures are substantially reduced when over drilling is eliminated and correct sharpening practices are followed.

Here are a few things to consider to keep energy utilization optimized and to get the most out of top hammer tools.

If drilling through abrasive materials such as sandstone and quartzite the wear tends to be greater on the bit circumference. Drillers should consider bit replacement or restoring the gauge button-to-body gap to original (new) condition.

When drilling in non-abrasive materials, carbide wear is minimized and drilling intervals are possibly longer. This allows for continued chip removal around the bit and wears away the bit body quicker than the carbides also referred to as body wash.

Similar wear occurs in fractured and loose formations where constant hole cleaning and re-drilling of the materials is required for stabilizing the hole and to keep the hole open during retraction. To prevent button loss or shearing under these conditions, the protrusion should be reduced to the original height by scheduling grinding intervals.

To use top hammer tooling effectively and get the most life out of tooling, it is recommended to work with a technical representative. A good technical rep will help establish specific guidelines for maximum suggested life of the bits.

To purchase the most advanced and reliable top hammer tooling, look for companies that have developed the tooling over decades of experience and continue to improve the products they offer.

It is always important to care for and maintain tooling and equipment. Consider training and regularly reminding drillers on how to get the most life out of top hammer equipment. More often than not, drillers come to work to do their very best and everyone wants to improve. Share these tips and top hammer drilling productivity will increase.

This article appeared in Rock Products.

It is helpful to understand the reason deviation occurs. If drill bits rotate perfectly on a central axis, the direction of advance does not change. However, the mechanics of percussive drilling prevent perfect rotation. Radial crushing of rock and repeated rotation create a hole larger than the bit diameter. With normal rotation, the bit gears itself against the hole wall. If continuously forced toward the same side of the wall, overbreak occurs and the bit naturally wanders in that direction.

The problem is more pronounced with horizontal holes. Gravity creates sagging in the center of the string, pointing the bit upward and forcing it to rotate off-center. In addition, the weight of the string causes the bit to pivot. Combined with counter-clockwise rotation, the bit is continuously forced to the left side of the hole and tends to wander up and left.

Poor drilling practices and ground conditions compound the problem. Here are the most common factors in hole deviation and general fixes. More specific guidelines can be found in our downloadable presentation.

Hole collaring presents the highest risk of misalignment in the drilling cycle. When collaring, the bit is not supported, so it tends to “skate” across the surface. Uneven rock surfaces cause bending stresses and the potential for the bit to tilt off-center.

Take time to set up accurately and collar correctly.

Excessive feed pressure causes the string to bend, thus tilting the bit off-center. The downward force of the string weight and feed pressure cause the bit to pivot during rotation. This motion continuously forces the bit to one side of the hole, resulting in deviation.

Use no more feed pressure than necessary.

In banded ground (successive hard and soft layers), the bit tends to turn into the softer layers. In fractured ground, the bit tends to follow the path of least resistance and follow fissures.

Maintain the correct feed pressure. 

Certain kinds of rods or bits can help reduce hole deviation.  For example, cross bits tend to drill a straighter hole than button bits; however, they can be significantly more expensive.

Choose products only after assessing the opportunity cost of not drilling straight holes as well as the potentially greater and more cost-effective influence of drilling practices. 

Excessive thread wear results in excessive play between mating components and increases the risk of deviation. In addition, dull bits tend to deviate more than sharp bits.

Avoid drilling practices that result in premature thread wear, and regularly check equipment for excessive wear.