Blasting Through the Ages: A brief history of drilling

By |  June 11, 2020
An underground drill jumbo is an example of percussive drilling. The first mechanized percussive drill was invented in 1844 using compressed air to apply the percussive load to strike the drill. Photo:

An underground drill jumbo is an example of percussive drilling. The first mechanized percussive drill was invented in 1844 using compressed air to apply the percussive load to strike the drill. Photo:

The Blasting Through the Ages series is an initiative by Pit & Quarry and Academy Blasting to tell the story of the blasting world. Throughout the ages, great blasters and engineers revolutionized blasting to the science and art used today. The series will detail the historic methods of drilling, loading and blasting, as well as take readers throughout history to touch on major developments through the ages. The series begins with a brief history of drilling.

Editor’s Note: This series was originally published in June 2020.

A small gold mine in Hungary began an experiment in 1627 that changed mining forever.

Feb. 8 was a cool, crisp morning that year in the Hungarian countryside as miners descended into the earth. But this day was different.

Caspar Weindl led the group, which was being observed by the Hungarian Mining Tribunal, and had a new idea that would be tested.

The crew of Oberbiberstollen of Schemnitz would attempt to break the rock and gold, not with fire and vinegar, but with black powder. It began by using a striking rod with a large hammer, forcing horizontal holes into the face of the drift and, afterward, filling each hole with small amounts of black powder. Then, a reed filled with black powder was placed into the hole, and a wooden plug was inserted into the end to keep everything tight.

Weindl lit the reed, and the crew ran for cover. The air hit their chests with a large thud, the ground shook for what seemed like ages and the man prayed hoping the crew would make it out of the mine.

When the dust settled, everyone looked to see what destruction lay in the wake of the blast. They found rock – not massive rock that would take days or weeks to break, but finely broken pieces of rock that could be brought to the surface for secondary breakage.

On Feb. 8, 1627, a new age dawned on the mining industry: the age of blasting.

Drilling’s story begins

Modern hand steel shows how miners originally placed holes. Photo: Ryan Sibley

Modern hand steel shows how miners originally placed holes. Photo: Ryan Sibley

The story of drilling begins in these early mines of Hungary and Germany, before the technology of blasting had been taken to the rest of the world.

The Hungarian and German miners took large striker bars (chisel) and beat in holes with large hammers that were about 2 in. in diameter and about 40 in. in length. The holes were then loaded with about 16 grams of black powder and detonated.

This was not an age of optimization of blasting. The focus was on completing the job and spreading the technology to other mines. Drilling a hole would take a crew of five men – one who would hold and turn the striker bar, three men with heavy sledgehammers who would take turns striking the bar, and one man who was on break. The entire crew rotated to ensure they stayed active and did not get too worn down.

While innovations such as clay tamping (stemming) and powder factor were developed, the next major change to the blasting environment came from improving drilling capabilities.

The first new drilling technology came in 1683, when Henning Huthmann proposed a new drill system that used gravity to drill holes. This drill could only be used on vertical holes (such as shafts and open pits mines have) and the drill steel would be pounded into the rock to start.

Two “strong men” would then pick up a heavy weight that was held in place on a rope frame, lift it high and drop it onto the striker bar. It was reported that only 10 blows would be required for the drill 1.5 in. deep – and it is easy to see how slow and laborious production was at this time.

This was known as the drop drill, a category of drill that relied on dropping a weight onto the back of the steel while slightly rotating the steel to cause the drill to advance. This is a similar mechanism to drilling that is used today – percussive drilling – but was labor intensive and typically required a human to pick up the weight and release it.

The drill’s bits of the day were crown and cone bits, which are slow and inefficient at breaking rock. Holes were not flushed with air or water to remove cuttings and all drilling relied on striking blows.

In 1749, Hungarian miners introduced wedge bits, and a decade later the Germans introduced the chisel bit. These helped to increase efficiency but still did not solve the problems with drill cuttings.

Further research identified that a combination of the number of strikes and the weight being dropped on the back of the drill both contributed to the speed of drilling. Experimentation was being done worldwide on the “ideal” weight for the drop-drill system.

In 1840, a new method of drilling technology emerged: rotary drilling. This system relied on a man turning, by hand, a drill steel that would slowly work a hole into the rock. This system was originally only used in coal and very weak materials, as the pressure and speed of rotation were not fast enough for good penetration in hard rock.

Before this time, the only machine drill was the drop-drill for vertical holes. So this system gave miners the ability to easily and quickly drill boreholes underground.

In 1844, the first mechanized percussive drill was invented by Brunton, using compressed air to apply the percussive load to strike the drill. This was later developed by Nasmyth, and the mining community now had access to an easy method to drill horizontal holes with compressed air: percussive drills. This technology was quickly advanced by those such as Schumann, Cave, Couch and Burleigh, developing what we know today as the jackleg drill.

With surface mines wanting larger-diameter holes than the 1.25-in.- to 2.25-in.-diameter holes that were used underground, rotary drilling began to advance. Originally, the goals for hole diameter became 4 in., then 6 in., and they’ve continued to grow through the ages.

At the same time, drilling deeper holes became imperative with the invention of dynamite. With black powder, charges had to be short to properly work and long drill holes were not necessary. With the invention of dynamite, everything changed and drilling technology had to keep up.

The drop-drill system was great for vertical holes in shafts, but it could not keep pace with mines’ desires for larger-diameter holes. The drop-drills were also not very portable, and rotary drills began to take over.

These drills could be a larger diameter and portable, and initially were operated by a system of gears to allow a man to sufficiently drill out a blast. Eventually, these moved to having the drilling mechanized through inventions of Armstrong, Keystone and Downie. These drills led the movement toward modern, large-diameter rotary drills that are available today.

Current state of drilling

While a book could be written on the history of drilling and the various types of drills that were invented, this brief analysis tells the story of drilling from the first borehole that was placed into rock for blasting to the start of today’s modern drilling systems. So let’s make a brief jump ahead in time, then, to the drill systems that are used in the mining and construction industries today.

Three major classifications of drills exist. The first and most common system is the top hammer drill. This is a percussive system that operates by a percussive, striking blow at the top of the drill steel. The fast strikes and quick turns of the steel allow for rapid drilling. This system is similar to the ancient drop-drill systems that operated using the same basic mechanics. The top hammer drill’s typical bit size is 2 in. to 4 in. and has a maximum practical depth of about 60 ft.

The second system is the down-the-hole (DTH) hammer drill, which has a percussive drilling style but has the striking action placed immediately above the drill bit. This allows for drilling much deeper boreholes that can extend over 300 ft. into the earth. These also do not have a decrease in penetration depth.

These drills can also function in larger-diameter boreholes, and the typical bit size ranges from 3.5 in. to 10 in. This is a great advancement on the percussive technologies to allow deeper, more accurate holes at a larger diameter than the top hammer. For this reason, DTH drills have taken over a large part of the marketplace for mining drills in medium to hard rocks.

The third system currently in the marketplace is rotary drills, which operate similarly to the rotary systems of the late 1800s and early 1900s. They use a large and heavy downward pressure to keep the drill bit in contact with the rock and slow claw away at the rock mass, placing large-diameter boreholes. These drills have minimal borehole deviation, as they use large steels that are threaded together to drill the rock.

In hard rocks at large diameter, they typically use a tri-cone bit, which gives up to a tenfold increase in drill rate to drag bits and can reach up to 17.5 in. in diameter. These drills are the workhorses of the large surface mining industry.

The future of drilling

No story of drilling is complete without a look at what is to come in the drilling world.

Today, improvements not only are advancing in drilling equipment but in the accompanying software used. Modern drills are advancing to being self-sufficient without the need for an operator in the cab. These drills are auto-positioning and automatically drilling a hole to the exact depth that is designed – and this is no easy task for a human operator.

Drills today are automatically recording key parameters such as penetration rates to develop automatic borehole logs to help understand the rock. This technology is likely to advance into fully autonomous drilling fleets on sites that are not only developing information on penetration rates, but are automatically sampling the rock to give properties such as compressive strengths, tensile strengths and Young’s modulus.

This can help the blaster to optimize hole loading to get better results, but it can also be used by engineers to delineate different grades of rock and ore. In the future, these drills may even include sampling systems to automatically report the grade of rock/ore that is being drilled.

While drill holes may be able to work toward larger diameters, the question needs to be asked: Do we really need larger diameter holes? A 17-in.-diameter borehole would need a bench height of at least 125 ft. to efficiently break rock. The lowest cost and best performance of a blast with a 17-in.-diameter hole would require a bench height of 165 ft.

Very few mines in the world today could realistically see a benefit from larger diameter. The majority of mines operate at much smaller than this maximum.

While larger diameters are possible, it is not something that would be beneficial. Additionally, as more mines are going underground and using smaller-diameter boreholes, this would likely not be a market that is feasible.

The next upgrades in drills will be in efficiency. Currently, the market is rapidly increasing the efficiency of the drill bit itself.

Combine this with more robust equipment to reduce overall drilling costs, and you’ll see competition for the future of drilling equipment center around cost of ownership, reliability and efficiency.

In the future, drilling will likely move to be electric and powered by large batteries, but this is perhaps 15 to 30 years off for widespread implementation in the industry, with the current rate of advance of battery technology.

Lastly, these questions should be asked: Do better drilling methods exist? Will we continue to use percussion and rotary drilling techniques for the foreseeable future? To understand this, the past must again be explored.

Systems such as the jet-pierce, which used thermal fragmentation to break rock in the hard rocks, were extremely expensive to use and quickly replaced when tungsten carbide bits came to market. The system of laser drilling is inefficient because of the large power draw and fluence requirements, and is unlikely to become a major method of drilling in the marketplace.

Using explosives to drill has also been successfully accomplished, but this faces problems with efficiency and application. While many other drilling technologies have been studied, it is difficult to beat the reliability, ease of use and practicality of percussion or rotary drilling.

Perhaps in the distant future we will see other technologies such as thermal fragmentation be developed to change the face of drilling. For now, this seems to be a ways off.

Finishing the story

After nearly 400 years of drilling, history has seen significant enhancements of the practice and trade of boring holes into rock to make way for mass breakage.

This history is one that could never be fully captured in a few short pages, but it is clear to see that the industry has completely changed since that first blast in 1627.

The story of drilling started with men who labored their lives away, chiseling holes in rock. And it ends today with machines that move and drill on their own without so much as a person sitting on top.

The industry is set up to experience great strides in advancements over the next 20 years, redefining what drilling looks like. It has shaped for great new innovations over the next 400 years, when future miners will look back and be amazed by the “old school” ways of drilling today.

What’s next in the Blasting Through the Ages series

Part 2. Explosive Advancement Through the Ages

Part 3. The Evolution of Initiation Systems

Part 4. Blasting: The Story of Breaking Rock

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