Show DRILLING AND DRILLING EQUIPMENT by arthur jarman mining engineer in detonator hand methods are still used in out of the way places such as in developing a prospect and in special circumstances where it would not pay to install machinery certain principles were established by hand methods that have been adhered to in machine work for instance the action of the hammer and gad is applied in the pneumatic chisel single handed drilling may be likened to that done by the pneumatic hammer drill double handed drilling to that ot of the lighter piston drills while the jumper principle is is applied to the heavier machine drill operations were at first laboriously conducted with pick and shovel from the pick the miner evolved the gad which is merely a small pick that has one end cut off so as to tg present a hammer face the handle is held so that the point of the gad is in contact with theore the ore or rock and the hammer end of the tool is then struck with a hammer which is wielded in the other hand in this way a blow is given with the point of the gad exactly where required most of the early mining having apparently been done in chisman this manner the hammer and gad have haye been adopted as the badge or crest of many mining societies early methods of mining the writer when working in lead mines at halkyn in Flint shire wales visited a mine that only ranked as a prospect a hand operated jig being its sole means of concentrating any ore extracted yet a visit underground 6 was full of interest for the old workings were believed to date back aback to roman times and were very extensive they were first encountered more than two hundred feet from the surface and the original b point of entry had not yet been discovered it took several hours to walk crawl and wriggle through these parts of the old workings that were believed to be safe to enter the ore body was a lode that was almost vertical and varied from six inches to three or four feet in width only mineral bearing rock had been excavated the hard limestone walls being left intact throughout and the result was a very irregular space sometimes so narrow that we could not squeeze through throng g h it on all walls the marks showed clearly that a tool had been used with a point like a pick in many places the walls were blackened by smoke but this was probably due to the use of torches and not to the use of fire as is sometimes supposed it is well known that the excavation of rocks may be assisted by fire and this has been supposed to have been used by the ancients in mining after heating rock to a fairly high temperature if water be thrown it the sudden upon cooling will cause it to crack and split many rocks may be readily broken in this way the action is seen in nature in rocky chasms where the fierce heat of the sun bakes the rocks and the cold night causes them to crack and break giving rise to heaps of talus at the foot of the cliffs while it is possible that fire may have been used by the ancient miners for such a purpose it is unlikely for there is no evidence of provision for ventilation in these old excavations and without some means of exhausting the fumes from the fire the air would soon become so highly charged with fumes that the miners would be asphyxiated asphyxia ted A few experiences experience of this sort would soon convince even the most cold blooded of taskmasters task masters that the use of fire would be responsible for the deaths of nf his workmen the smoke marks are therefore due to the use of torches or of crude lamps probably relation of explosives to drilling the greatest advancement in drilling and mining methods were made when explosives were adopted for blasting biasing for at least a thou thousand sand years before gunpowder was known chisels or drills were used to make holes in large stone blocks to enable them to be raised and lowered into place by means of cranes such holes may be seen in the tops of huge blocks of stone that compose the ruins of ancient structures gunpowder was known in the middle of the century and 6 guns uns to utilize its explosive force for sporting and lor military purposes were developed in the century no doubt soon after this the miner found that he could confine gunpowder in a hole drilled in rock and explode it thereby shattering the rock when this was discovered the miner had stumbled onto one of the greatest advances of modern civilization the use of explosives for mining and quarrying rock and ore even with the low power of early gunpowder the work that could be accomplished by the use of the pick and gad was multiplied several times the output per man greatly increased the invention and use of dynamite and more powerful explosives again doubled and trebled the output per man especially when working t in hard tough rocks dynamite was invented by nobel in 1863 but miners were already using other explosives and were exercising all their ingenuity to devise machines that would economically bore or chisel the holes that were necessary hand drilling still has a place where the amount of work to be done is small or when the money is not available for machine equipment hand drilling is still used the procedure adopted depends upon the hardness of the rock the room available in which to work and the ability of the miners the hand method is also used where machine work would shatter the rock too much or where the undertake under undertaking taki ng would not pay to install machines in all hand drillen drilling 6 operations the drill should be rotated through a portion of a turn between strokes thus chipping pin za the rock away evenly so as to give a round hole uneven turning of the drill makes an irregular hole that tends to fitcher and jam the bit so that eventually it be becomes cornes impossible to turn the drill in which event the hole has to be be abandoned or else continued at smaller diameter by using 0 a smaller drill bit single handed or single jack drilling the miner holds the drill in position with one hand and strikes the top of the drill with a fairly heavy hammer 32 to 4 pounds wielded in the other hand when the hammer hand becomes tired hands are changed if there is is enough space for the hammer to be swung 6 when the miner changes his position the depth of hole hol e drilled by this method rarely exceeds three or four feet suitable for rocks that are soft or easy to drill but when hard rock is encountered progress is so slow as to discourage the men and the long time taken naturally increases any overhead charges b there may be if the hole is drilled dry frequent stoppages are needed to clean out the chips and rock dust that form otherwise the broken rock forms a cushion that prevents progress it is better to use water and if necessary should the drill become sticky clean out the mud with a scraper formed by flattening the end of a ya inch iron rod and then bending it at right angles to the stern stem the miner will find that ress is much faster than when drilling dry the fine rock is is sus suspended p ended in the water instead of lying at the bottom botto ni of oi the hole and cushioning the next blow of the bit an up and down motion is necessary when rotating the tn drill between strokes of the hammer this mixes the rock dust with the water an and d prevents the mud from cli clogging aging and making the drill stick A piece of canvas leather leathe r or thick cloth with a hole in it is placed around the drill to prevent splashing while drilling is in progress pumping out a drill hole etc if the mud can be kept thinner still better work can be done in hand drilling but some form of pump will be p advisable to draw out the thin mud the simplest form is is a piece of ya inch iron piping run to the bottom of tie t e hole to work such a pump place one hand on the top of the tube to close it from the air draw the tube up smartly about 18 inches take your hand off the top and shove the tube down a again 6 ain to the bottom of the hole quickly repeating the process this action pumps out the mud it being ejected on each down stroke after one or two strokes have been made not only in hand drilling but in machine drilling the progress made is enormously increased by the use of water and when a constant stream of water is forced to the bottom of the hole through the use of hollow drill steel the result is a wonderful improvement thus we find that the experience gained in hand drilling is applicable to machine drilling A large number of light blows may be made to do the same work as a smaller number of heavy blows on the drill it is necessary to rotate the drill in a regular manner in order to keep the hole cylindrical water is used to keep the dust and chips of rock in suspension and thereby keep the drill hit bit in close contact with the rock so that it can do its work instead of being cushioned by mud frequent cleaning out of the mud is needed in the same manner as in hand work but in modern machines the mud is flushed out by a continuous water stream in soft rocks that stick and clog the drill the hand miner moves the drill up and down when he turns it to mix the mud and prevent the drill from sticking in such rocks the reciprocating drill is better than the pneumatic hammer because without these motions up and down the drill may stick so tightly that it cannot be moved double handed drilling or two handed drilling A sledge hammer is used in double handed drilling which is so called because both hands are needed for the hammer one man holds the drill and turns it while his partner strikes with the hammer which weighs about eight to to ten pounds the greater intensity of the blow obtained by using a heavy hammer results in a correspondingly greater rate of drilling 6 the fact that two men are employed on one hole does not matter much because they take turns to avoid fatigue the use of a sledge hammer is only possible when there is enough room to swing it properly it cannot be used in cramped quarters without danger to the man who is holding the drill the depth of hole thus drilled is usually five feet and rarely exceeds six feet multiple handed drilling when there is plenty of space to swing 6 hammers two or more men may strike at the drill while another man ma n turns it this gives an even greater rate of progress but is only possible in big spaces and where speed warrants the arrangement as in sinking a shaft with two men striking it may take as much as an eight hour shift to drill seven or r eight feet in hard granite or diorite and about twice this footage would be obtained in a hard limestone at 4 per day the cost per foot would be in one case and for the other the jumper the jumper is a long steel drill with chisel bit that is used for vertical holes in quarry work the miner raises it in his two hands and brings it down smartly with an action like that used for a harpoon between each stroke and the next one ond the steel is turned through a fraction of a revolution in the same way as when hand drilling and for the same reasons water is used in the hole when pos sible to give more force to the blow the drill may have a weight the shape of an elongated ovals oval welded onto the shank 4 |