The ROCK DRILL and CIVILIZATION

THE PROGRESS OF MANKIND CAN BE MEASURED BY THE progress of mining and metallurgy. The successive historical epochs of stone, copper, bronze, iron, steel, and silicon are the steps our species has taken in the quest to control the world rather than simply survive it. Besides adding to humanity’s health and material well-being, each of these stages has created the need for an everincreasing web of laws, rules, and etiquette. The whole complex synergy that we call civilization ultimately depends on mining, and mining depends on rock drills.

The earliest miner was a prehistoric hominid who picked up a loose rock and used it as a tool to increase the advantage of his or her opposable thumb. He or she found glittering gemstones, gold nuggets, and pieces of native copper useful or at least decorative, and when the loose pieces lying close to the surface were used up, mining began in earnest. Salt, too, was an important mined substance in ancient times. Without its use in cooking and food preservation, little advance beyond hunting and gathering would have been possible.

In near-surface deposits, early humans could mine by simply finding loose hard rocks to beat on softer ores. But below a weathered upper layer, ore deposits generally became tougher. Metals were then pursued to incredible depths by artisan miners and slave laborers working in hellish conditions. They built fires next to an ore face to soften it, sometimes quenching the hot rock with water (or vinegar, which was thought to be more efficacious) to break a few pounds of mineral off the surface. Not only mines but other rock openings, such as the tombs of ancient Egypt and the tunnels of the Roman aqueducts, were undoubtedly excavated in this manner. Without forced ventilation, and with only limited comprehension of the gases produced, such work could be deadly.

The arrival of the Iron Age, during the second millennium B.C., improved people’s lives in many ways. It led to much more efficient plows, hoes, and other agricultural implements and to great improvements in wheeled vehicles and swords, shields, daggers, and other instruments of advancing civilization. Below the ground, iron metallurgy gave miners picks and bars, wedges and gads, tools hard enough to drive into natural cracks in ore and force them apart. More mines opened to produce iron, and more slaves were shackled to swing the picks and drive the wedges.

The old thermal-stress methods were retained for some uses, however, even in the most modern and progressive mines. Iron was still expensive and of variable quality, and much skilled labor was required to fashion it into tools and keep them in working condition. The Japanese were still using thermal-stress methods for long tunnels in the 1880s.

It took about three centuries after gunpowder became known in Europe before some resourceful miner, probably in the late 1500s, thought to stuff the powerful little grains into cracks in the rocks, ignite them, and let chemistry do the work of many hands and arms. The deeper the crack, the more gunpowder could be loaded and the more rock broken. Eventually miners realized that they could extract even more if instead of relying on natural cracks they used an iron tool to make a narrow, deep hole with a small outer opening that could be plugged to confine the combustion gases. The first documented use of drilling and blasting for mining was by Martin Weigel in Freiberg, Germany, in 1613.

As gunpowder greatly multiplied the rate at which ore could be removed, mines went deeper and deeper into the earth and metals began their long transition from luxury items to commodities. While great effort went into such problems as keeping the tunnels from collapsing and transporting workers, supplies, and rocks in and out of the mines, the whole process depended first and foremost on the men who drilled the blastholes. For three centuries their powerful arms ceaselessly swung hammers against iron (and later steel) drill rods. Each stroke pulverized a tiny bit of rock under the chisel tip. On the backswing of the hammer, the drill would be rotated (by the hammer wielder himself if he was alone, or else by a workmate) so that the next blow would drive the bit into fresh rock. Swing, turn, swing, turn was the endless rhythm, hour after hour, day after day.

Drilling a narrow, precise hole required much more from the tools, and thus from the toolmakers, than the brute-force methods of the pick-and-wedge era. Blacksmiths used all their energy and skill to keep miners supplied with sharp drills, and a constant stream of rods—sharp in, dull out- was carried through the mines by young boys called nippers. Every good smith had his secret hardening compounds and ritualistic tempering process, for hardness at the cutting edge was everything in the battle against the rock. As with gunpowder, the technology of war served the rock driller well, with blacksmiths adopting many advances from the fabrication of sword steel and armor plate.

In the hand-labor era, which lasted right up to early in this century, there were two kinds of hard-rock drilling: slow and slower, depending on whether it was done by a team of men or by one man working alone. One man swinging a four-pound hammer and holding his own drill rod was called single-jacking. A two-man team was called double-jacking. One man would swing a hammer that might have a nine-pound head while his partner held the drill rod as a steady target and gave it a quick twist while the hammer was going back. If the end of the drill rod wasn’t exactly where the driller wanted it on the next blow, the swing could be very hard on the holder. Trust in your partner was everything, and it wasn’t a good idea to do anything that might get him mad at you.

When the hammer man tired, they would switch positions, often in mid-stroke without missing a beat. A little water was usually added to downward holes to help flush out the cuttings, keep the dust down, and cool the bit to preserve its temper. With upward holes this was not possible, so they were drilled dry. Over the years the accumulation of dust in a miner’s lungs would gradually smother him, as his alveoli became plugged with insoluble silica particles. This was the dreaded silicosis, or miner’s consumption, usually just called “the con.”

Hand drilling is an extremely slow and grueling process, a severe test of strength and endurance. In very hard rock two strong miners might work 12 hours and make less than one inch of hole. Every old miner claimed to have worked in a place where the rock was so hard that the first shift had to work all day and then leave a man underground with his finger on the spot so the night shift would know where to continue drilling. In average rock one man might drill 8 inches an hour, while a two-man crew might make 2 feet. It would take 20 to 30 holes, 1 to 1½ inches in diameter, to be able to blast away enough rock to advance a 4-by-6-foot tunnel 4 feet. Drilling those 120 feet of hole might use up 200 pieces of sharpened drill rod over several days.

For almost 250 years this method was improved on only in the composition of the drill rods and the methods of tempering them. The cutting edge had to be as hard as possible to chip the rock, but not hard enough to shatter. Similarly, the rod had to be hard enough not to deform from the countless hammerblows, but soft enough not to break. Irons and steels from certain regions, especially in Sweden, gained favor because of naturally occurring alloying elements such as chromium or nickel in the iron ore. As metallurgical knowledge increased, smiths learned to duplicate these materials by adding secret ingredients to their alloys.

This period, the late Iron Age, which actually lasted well into the Industrial Revolution, was the grade school of mankind. Human and animal power, with occasional assists from wind and water, performed most of the labor required for survival. As the Middle Ages and the Renaissance gave way to the early modern era, iron tires and gears, nails and fittings, tools and instruments all were making life easier. Progress in mining was also accelerating the growth of international trade. It did this in several ways: by making travel faster, easier, and safer; by expanding the array of manufactures that could be used as trade goods; and by increasing the supply of precious metals, which lifted local and world economies beyond the barter system. But these processes of growth and change remained slow, and hand drilling continued to satisfy the needs of mankind’s endeavors.

In the first years of the nineteenth century, the steam engine accelerated this calm pace forever. Suddenly one engine could do more work in a dav than a small village had done before. The demand for iron and other metals, as well as coal, to feed this industrialization was tremendous, and mines became the vanguard of many new technologies. The world’s first practical steam engine was used to pump water from a mine. The first practical locomotive pulled cars in a coal mine. Steam hoisting engines, along with the pumps, allowed miners to reach ores that had formerly been too deep to recover.

These and other aspects of mining saw much progress, but in the end everything still depended on the rock drill. One analysis attributed two-thirds of total mining costs to the drilling of boreholes. And since mine owners found themselves hard Dressed to eet enough arms swinging hammers to drill all those holes, the search for a mechanical drill began in earnest around the middle of the nineteenth century. The earliest attempts were cumbersome steam-driven machines for drilling holes in canal construction or open-pit mines. They were complete failures. The machinery had to be kept close to the boiler, since steam loses much of its heat and pressure when transported over long distances. No successful high-temperature, highpressure hoses were available for flexible connections. Open space was also needed to allow for the dissipation of waste heat and water vapor. All these considerations made steam impractical for most underground mining.

Mining wasn’t the only industry that needed a good mechanical rock drill. Beginning in the 1830s, railroads gave promise of bringing the United States closer together by spanning the prairies and crossing the mountains. But in order to do so, they needed to maintain moderate grades and curvatures. Mountains would be impassable barriers without long tunnels through solid rock.

The first true mechanical rock drill of record was designed and built in 1848 and patented in 1849 by Jonathan J. Couch of Philadelphia. It was large and unwieldy and far from a commercial success. Couch had been assisted by Joseph W. Fowle, but the two men parted company before the patent was issued, and Fowle patented his own drill within two months. In 1851 Fowle patented a new design that was the seed of the modern rock drill. It was the first to use a flexible hose that made the drill independent from the boiler, and it later pioneered the use of compressed air for power transmission. Unfortunately, while Fowle had imagination and vision, he did not have the financial resources to carry his design forward. Between his 1851 patent and 1866, only 12 U.S. patents relating to rock drills were issued, including a second (and last) by Couch in 1852.

The first moderately successful rock drills appeared in the 186Os, their development spurred by the agonizingly slow progress that was being made on two major railroad tunnels: the 24,000-foot Hoosac Tunnel in Massachusetts and the 44,100-foot Mont Cenis Tunnel through the Alps between France and Italy. These were monumental projects, greatly exceeding anything that had been attempted before, in rock of unyielding toughness.

In 1854 the Massachusetts legislature passed an act to assist construction of the Hoosac Tunnel in the northwestern corner of the state. (Ground had been broken in 1851.) The state lent its credit to the extent of $2 million (the equivalent of about $30 million today) for the projected $3.35 million enterprise, an arched tunnel 24 feet wide and 21 feet high. The tunnel was expected to be finished in a little more than four years.

It wasn’t. False starts were made by a number of different contractors, some of whom had to raise the money for the work themselves. After nine years the total progress amounted to 4,250 feet, less than 20 percent of the project, all of it by hand drilling. Several novel machines, both rock drills and fullface boring devices, were tried. One of them was supposed to carve a ring 13 inches wide and 24 feet in diameter into the face, after which explosives would loosen the core. The 75-ton device, powered by a pitiful 100 horsepower, advanced all of 10 feet before finally being scrapped. Like all the other machines that were supposed to make the excavation a snap, it was no match for the tough gneisses and schists of Hoosac Mountain.

In October 1863, after a succession of bankruptcies, the Commonwealth of Massachusetts took over. Partly because of the Civil War, little was accomplished until 1865, when about 550 feet of tunnel was completed. (It is difficult to measure progress precisely because the Hoosac was constructed in stages. First an initial small bore was driven; then it was enlarged to the final cross section; and finally the sections were arched with masonry. In written accounts, progress is usually given as the advance of the pilot hole only. Thus months with no apparent progress may have been spent on enlargement or other work.)

Between 1863 and 1865 the state made several attempts to introduce rock drills into the tunnel, and in June 1865 a flume and penstock were completed to provide waterpower to air compressors. The most successful of these early experiments was the Brooks, Gates, and Burleigh drill, which was developed for the tunnel and first tried when the compressors became available in June 1866. While not a success, it did serve as a steppingstone. The machine weighed 240 pounds and consisted of 80 pieces. It cost $400 in the days when a good Colt revolver could be had for $10 or less. The longest recorded use of such a drill was five days, and even two consecutive days’ use was considered exceptional. Nothing on the machine stood up to the abuse of hitting solid rock 200 times a minute. In four months 1,084 drills were sent out of the heading for repairs, or about 10 a day. To keep 5 or 6 drills in the face, 40 were required. One account of the drilling effort said that “the tunnel seemed to be a highway, along which a crowd of people was continually passing, each person carrying a portion of a drilling machine, or tools or materials for repair.”

The air compressors were only slightly more dependable. They relied on water injected into the cylinders to cool the heat of compression and seal the pistons and valves. Occasionally excess water demonstrated its incompressibility and the machine spontaneously disassembled itself. Furthermore, compressing air for power transmission is inherently wasteful, and as little as 10 percent of the energy applied to the compressor was delivered at the rock face. But waterpower was plentiful and cheap, and drillers appreciated the constant stream of cool, fresh air—especially when compared with the sticky heat created by steam power.

Charles Burleigh fell out with his partners early in the tests and refined the design on his own, buying the Fowle patent to avoid litigation. (Burleigh had helped build the original Couch/Fowle drill as a machinist in Fitchburg, Massachusetts.) He continued to improve the machine and came up with an entirely new drill that was placed into service on October 31, 1866. The new drill was nearly as complex as the partnership-designed machine, but it transferred the stress to stronger components. The whole assembly was bulked up, weighing 372 pounds. While it drilled at about the same rate as the old model, it was much more durable. One exceptional machine worked two and a half months and drilled a mile of hole without a breakdown. Only two or three machines were needed to keep one in the face. The progress of the tunnel increased from 570 feet in 1866 to 1,187 feet in 1867. (The replacement of black powder with much more powerful nitroglycerin also played a big part.) During 1871 workers drove through 1,743 feet in 10 months with a newer-model Burleigh drill. The headings met in November 1873, and the tunnel opened to traffic in February 1875.

The Hoosac Tunnel demonstrated that powered rock drilling had crossed from the experimental to the practical. Once it was shown to be possible, everyone started doing it, though the speed of its adoption varied widely by industry. The new technology saved enormous amounts of time but not necessarily money, especially where cheap labor was plentiful. Tunnelers were quicker than miners to adopt the new technology, since speed of completion was generally more important than keeping costs down; mine owners, especially small ones, lagged behind in modernizing their operations. For quarrying and surface extraction, which were conducted in the open air, the simpler and cheaper technology of steam power held sway much longer.

In Europe, meanwhile, work on the Mont Cenis Tunnel progressed slowly with hand drilling from 1857 until 1861, when machine drills designed by Germain Sommeiller, an Italian engineer employed on the tunnel, were put in service. These machines used compressed air provided by hydraulic rams at a pressure of 9 psi (modern drills operate at 100 psi), and 200 drills were needed to keep 20 in the faces. They were heavy, awkward tools mounted on carriages that had to be rolled into and out of the tunnel on rails, but they were still three times as fast as hand drilling (at two and a half times the cost). The Sommeiller drills were used for the entire tunnel until completion nine years later, with modest improvements taking place over that time. By the end the Sommeiller drills were advancing at five times the rate of hand drilling. The tunnel’s two headings met on December 25, 1870. Without power drills, they would have taken 40 or 50 years to converge.

European drilling progress stagnated after the introduction of the Sommeiller machines, and by the mid-1870s Continental hardware was years behind that of the United States. American technology was making rapid progress in related fields as well. Metallurgy was shifting from an art to a science, with superior cast iron and steel coming into use. Air compressors became more reliable, and pressures climbed from 35 to 80 psi. Nitroglycerin was replaced by much safer dynamite, and fans were built to provide fresh air to deep tunnels. In spite of its early dominance, the Burleigh Rock Drill Company lagged behind newcomers like Rand, Ingersoll, Sergeant, Wood, Waring, Blatchley, and McKean. Still, for many years miners referred to all pistonstyle rock drills as “burleys.” In 1872 Burleigh sold out to Ingersoll, which in turn merged with Rand into a company that bought out many small firms and continues as a leader in the field to this day.

All these drills were of the piston, or “slugger,” type, in which the drill rod was firmly clamped to a piston that traveled somewhere between 2 and 10 inches—the harder the rock, the shorter the stroke. The drill rods were solid, and the cuttings were removed by the plunging action of the drill. After the early 1870s all machines rotated their drill rods with a spiral “rifle bar” at the rear of the piston. At 60 psi of air pressure, these drills ran from 200 to 600 strokes and penetrated two to six inches per minute. All were firmly mounted on columns, tripods, or carriages to support their weight and resist the forces of recoil. Workers made sure to install their drills firmly to keep the mounts from falling on the careless user.

As the appetites of civilization continued to increase, miners were forced to dig deeper for more metals. Electricity for communications, lighting, and power created an unprecedented demand for copper. Iron and steel became the most important materials for suspension bridges, suboceanic cables, transcontinental railroads, oceangoing ships, and huge machinery, the showpieces of civilization.

In the 1890s, as metallurgists developed steels that could be heat-treated to resist deformation, a new type of machine evolved: the hammer drill. In this variant—a mechanical analogue of old-fashioned hand drilling—the drill rod slid freely in a chuck while a piston hammer struck its end, either directly or through a tappet. Without having to move nearly as much mass as the piston-type drill, the hammer drill could operate at around 1,400 strokes per minute, delivering sharp, fast blows to the rock. These hammer drills were light-duty machines, best adapted to drilling upward holes. They were not suitable for downward holes because there was no way to get rid of the cuttings, which made a powder that cushioned the blows. Because of their high speed, these drills were known as “buzzies.” Later, as the fine dust they produced built up in workers’ lungs, they were called “widow makers.”

Adapting techniques and metallurgy originally developed for boring gun barrels, hollow drill steel was developed in the late 189Os, primarily by J. George Leyner, a Colorado entrepreneur. He used the latest high-impact steels to build a heavy-duty hammer drill that could work in any direction by evacuating the cuttings with a jet of air through the center of the drill rod. The machine was an immediate success, and Leyner sold about 75 of them.

Unfortunately, high-pressure ejection of extremely fine rock particles compounded the dust problem, and miners refused to use the new machines. Leyner met the problem head-on by recalling every drill his fledgling company had built and retrofitting them all with an ingenious needle through the center of the piston that injected water through the drill steel, wetting down the dust. Still, the episode made mine operators, a habitually conservative bunch, slow to accept Leyner’s innovation.

After World War I the hammer-type drill almost completely supplanted the piston drill, as all manufacturers began building them when Leyner’s patents expired. The “jackhammer” hand-held pneumatic drill became a fixture at every mine and construction site. These drills were often powered by portable air compressors that were a far cry from the massive, inefficient water-injected machines used at the Hoosac Tunnel. By the 1930s the basic design had become standardized and the major drill makers’ machines differed only subtly from one another.

With drilling mechanisms working efficiently at last, the drill stem and bit became the weak link in the system. In a large mine or tunnel job, tons of drill steel still had to be hauled in and out of the workings every day to keep sharp tools at the face. Many attempts were made to build a detachable drill bit so that the long, heavy drill rods could stay at the working face with only the tips being replaced. In 1918 A. L. Hawkesworth, a mechanical foreman for the Anaconda Company in Butte, Montana, developed a bit with a dovetail joint to the drill steel. It was the first successful removable cutting edge. Later versions were threaded together, followed by a simple tapered friction joint for lighter drills.

The Carlton Tunnel, driven at Cripple Creek, Colorado, between 1939 and 1941, shows how much progress had taken place in the 70 years since the Hoosac. The first mile was driven in 121 working days, the second mile in 108. The best single month’s advance was 1,879 feet, more than the best year’s work under Hoosac Mountain and with less than a third the manpower. Of course, not all the credit goes to drilling science. At the Carlton workers had telephones to order supplies and trucks to deliver them. Electric-powered machinery and mechanical loaders mucked up the blasted rock, and locomotives instead of mules hauled it out. Powerful air compressors and ventilation fans, as well as bigger, healthier workers, all played a part. Within a few years advances of 100 feet a day were being posted in mines and tunnels.

After World War II the hand-held jackhammer was flexibly attached to a light air cylinder and the Jackleg drill was born, allowing a single miner to drill in any direction without a mounted drill. The new machines weighed around a hundred pounds and could drill two or three feet a minute using the new tungsten carbide-tipped drill bits. In larger tunnels improved hydraulics were showing up in the versatile drill “jumbos,” which allowed one miner to control several drills on a wheeled mount. In the 1970s hydraulic technology was applied directly in the rock drill itself, instead of being used to create the compressed air that powered the drill. This development made air-powered drills obsolete for most heavy mining and tunneling applications and allowed penetration rates of five feet per minute or more. (There is, of course, a much wider range of rock drilling and boring equipment. Surface mining, tunnel boring, highway construction, well drilling, and geological exploration are but a few of the areas that have developed their own specialized apparatus. But their inclusion here would make a book, not an article.)

Even down to the most mundane items, our world is built on materials taken out of the earth, from talcum powder to diamonds, gravel to silicon. The infrastructure of our cities depends on huge rock tunnels to bring water in and take waste out. Building foundations and sublevels are blasted into bedrock. At some point all transportation, from deeper shipping ports to longer aircraft runways, requires a major modification of the rocky face of the earth. Without advances in rock drilling, which have both fed and been fed by the Industrial Revolution, the cost of our modern civilization would be prohibitive.

Larry C. Huffman, P.E., is a mining engineer who lives in Butte, Montana.