Updated version tells tale of diamond core drill

To the diamond drill fraternity, the story of the invention of the core drill in 1863 is a familiar one. For those unfamiliar with the story, it bears retelling.

In 1857, the project of drilling a railway tunnel through the base of Mount Cenis in the European Alps began and when completed in 1871, formed a railway link between Modane, France, and Bardonecchia, Italy. The driving of this tunnel, known as the Mount Cenis Tunnel, was a major engineering feat of that time, being 7.98 miles long with a horseshoe section 26.25 ft. by 24.58 ft. During the first four years, the drilling was done by hand; consequently, the progress was extremely slow, nine inches per day on each end of the tunnel. After the fourth year, compressed air percussion drills were introduced which increased the progress fives times.

To a French engineer named Leschot, engaged on the project, this increase of progress and the means of obtaining it was still not satisfactory, as he explained in the following statements:

The apparatus invented by different engineers consists generally in implants of percussion set in motion by mechanism. In those most used, the boring tool is directly attached to a piston rod of a steam engine or of a compressed air engine; on the machine being set in motion, the boring tool is thrown with force against the part which is to be bored and that by successive percussions the required effect is produced.

These means, although they consume a considerable amount of power, are generally effective when used in rock of medium hardness, but their success is indifferent when employed in really hard rocks such as quartz and feldspar which, being harder than steel, soon caused the tools to lose their form or break.

Moreover, few companies can support the expense necessary for the compression of air and so are deprived of the effects which might otherwise be obtained from the application at the end of the tunnel of a considerable mechanical force. Here, therefore, is a deficiency which I have sought to supply. In designing the perforator, I propose no objects to obtain rapid preformation coupled with the employment of the least possible force, and thus beneficially to utilize manual labor. The possibility of reproducing mechanically the well directed work of the intelligent miner, that is of having the power to form the perforation so as to profit by the configuration of the rock and the course of the veins, thus obtaining the greatest amount of excavation possible with the smallest number of perforations and consequently the minimum expenditure of labor and powder.

His last statement certainly has a modern ring to it.

Leschot’s rock perforator was the “granddad” of all diamond core drills as it was used in the Mount Cenis Tunnel for drilling blast holes. It is interesting to note that the modern gear feed swivel head embodies the same principle of attaining a feed as was used by Leschot in his original drill, complete with a left-hand feed screw for fast retraction. With a belt drive, transmitting about one-half horsepower, Leschot was able to drill 4.6 ft. or more per hour through granite using black diamond to cut a 1.38-inch diameter hole.

Although Leschot designed this machine for drilling blast holes, it was soon realized, because of its core recovery functions, that it was destined to play a more romantic and thrilling role for man by probing many thousands of feet into the locked-up secrets of the earth’s crust, to discover and bring to surface cores of hidden ore bodies of great wealth on silver islet, not far from Port Arthur on Lake Superior, only 10 years later and nearly half-way around the world from the Mount Cenis Tunnel.

The design and development of diamond core drilling grew rapidly from Leschot’s first design of the hand-powered drill, to the steam-powered drill, to the steam-powered engine that were used for many years before the internal combustion engines. The steam engine used to power the diamond drills was a 2-cylinder “V”-type mounted directly on the boiler and the complete unit was mounted on two wheels. Besides the power developed by the steam engine, it also required 2-man power to feed the boiler with wood.

The diamond core drill of the 1900-1925 era made by the Sullivan Machinery Co. was driven by a 20-HP steam engine with a single cylinder hydraulic swivel head operated by high-pressure water from a separate water pump. The capacity of this drill was between 1200 ft. and 2500 ft. of 2316 inch hole, recovering a 2-inch core; the drill weighed about 4 tons.

In 1929, L. Jessen (who was a partner in Boyles Bros. Ltd.), realized that the diamond drills that were available then were much too large and heavy for the mountainous terrain of British Columbia. So he set to work and built the forerunner of a light portable diamond core drill using the hoist and swivel head from the steam drill and the engine of the famous Model T Ford. This drill weighed 1,400 lb. and could drill to 1,500 ft., recovering a 1316-inch-diameter core. At the same time, Jessen built a small drill for prospecting that could drill to 150 ft. recovering a 34-inch-diameter core and could be backpacked by a man.

He also built a light underground drill that was powered by a 2-cylinder double-active “V”-type compressed air motor. This small drill had a capacity of recovering a 1516-inch diameter and weighed only 550 lb. A large number of Model BBS-2 drills were used during the Second World War by the Royal Canadian Engineering Tunnel company. After the war, improvements in the design of the diamond drills gathered impetus, mainly along the lines of increasing the depth capacities of surface drills by installing larger engines, without an appreciable increase in weight and with an expanding use of high-speed diesel engines to reduce fuel cost.

The design of underground drills was affected by a trend back to the original work for which it was intended by Leschot, that is, blast-hole drilling. Because blast-hole drilling was generally considered a high-ball job, high-speed drills were involved to meet these new demands as well as quicker methods of handling drill rods.

The design of the surface core drill took a big jump forward by the replacement of controls which required manual effort with controls that governed hydraulic effort. This application of hydraulics eliminated many of the arduous and time-consuming functions of the operator.

Since Leschot’s conception of a diamond core drill in 1863, hundreds of millions feet of hole have been drilled the world over, discovering ore bodies worth billions of dollars. Although Leschot’s name may not be as well known as Marconi, Edison and the Wright Brothers, his inventions have been of benefit to mankind.

The past 30 years have seen tremendous strides forward in development of equipment for diamond core drilling, both surface and underground. Small, portable, lightweight drills still have their place in the diamond-drilling industry but with the more modern methods of moving equipment available today, weight does not play such an important role as in the 1940s and early 1950s.

The Otter and Beaver aircraft have played an important role in developing Canada’s north and still are common sights in remote exploration camps; however, they have been overshadowed by helicopters for moving drilling equipment and drilling personnel into inaccessible areas. Improvements to hydraulic components have made it much easier for companies to provide powerful and reliable hydraulic driver-core drills.

The hydraulic core drill as we know it today has evolved from having a power source that rotated a hydraulic pump, which in turn powered a hydraulic motor connected to the drive line. These systems were an improvement over the mechanically driven core drills.

It is an arguable point as to when the first hydraulic long stroke was made available, but it was not until the late 1970s that they became accepted in the drilling industry, and even then, most contractors were uneasy with the new hydraulic systems.

Today in Canada, it is probably fair to say th
at more than half of the drills operating are of the long stroke hydraulic type, and the number is even higher with underground core drills.

Longstroke hydraulic core drills may vary in choice of hydraulic components from one manufacturer to another, but they all have common elements such as surface drills having a minimum of a 10-ft. stroke and a hydraulic chuck which is rotated from a hydraulic-powered gear box. A rod clamp is essential for holding the rod string while the upper section is rotated during the making and breaking rod joints.

The use of a hydraulically operated hollow spindle chuck is most common in Canada; however, in Australia and in some parts of the U.S., the top drive or “plug drive” drill is extremely popular. These types of drills generally have other purposes than coring and can be used for hammer drilling or reverse circulation chip sampling.

Hydraulic rod handling drills have helped to keep drilling costs to a minimum by improving production rates and providing better core recovery results. The functions of these drills are synchronized to mover rods in and out of the bore hole using the least amount of effort from the operator. These types of drills have the capability to make or break the rod joints, thereby reducing the need of pipe wrench around the drill rods. The depth capacity of hydraulic rod-handling drills ranges from 500 ft. to more than 6,000 ft. in the Model B-20, by JKS Boyles.

The latest technology to be introduced into diamond core drills is the use of computers to control the drill functions. Computer systems have been used in machine shop equipment for several years but were never considered to be able to take the punishment of the harsh en-

vironment that the diamond drill operates within. Such systems are now available in the 1990s.

The operator can now touch a computer screen to dial in the drilling parameters or alter the functions as required during the drilling cycle. The rod running both in and out of the hole is controlled by the drill and the operator is required only to load or unload the drill rods.

The methods of rotating the drill string as well as making and breaking rod joints may have changed considerably during the 130-year period of the diamond drill, but the net result is still the same as what Leschot was aiming for: to take a sample of rock from deep in the ground with the least effort on the part of man.

Diamond coring bits are now lasting several hundred feet before the drill string must be pulled from the bore hole to replace a worn drill bit. This, combined with the new technology of heat-treated drill rods, in-hole tools and the long stroke rod handling drills allow the drilling contractor to work for nearly the same price per foot of drilling as 15 years previously and still make a small profit.

Who knows what the next big step will be in the development of the diamond core drilling equipment. One thing we can be sure of is that men will always be lured into the diamond drilling industry by the romance and challenges of drilling, and with God willing, I plan to be part of it for many years to come.

— Gary Pipher, the incoming president of the CDDA and vice-president of JKS Boyles International Inc., Orillia, Ont., updated this story on diamond core drill, written by the late J.W. Booth, by adding events during the 1963-1993 period.