Drill rig

“ The pipe vise belongs on a separate bench, which may be a plank bracketed against the side of the room.
Drill-Press.—The most satisfactory drill-press for use on a farm is the upright drill that bolts to a post. There is usually a self feed which may be regulated according to the work. The heavy flywheel keeps the motion steady, and because there is no bench in the way, wagon tires may be suspended from the drill block, so they will hang free and true for drilling. Often long pieces of straight iron are drilled with holes spaced certain distances apart. ”

“ Machine vs. Hand-Drilling.—The advantages of hand-drilling over machine-drilling lie, first, in the total saving of power, the absence of capital cost, repairs, depreciation, etc., on power, compresser Page 150 and drill plant; second, the time required for setting up machine-drills does not warrant frequent blasts, so that a number of holes on one radius are a necessity, and therefore machine-holes generally cannot be pointed to such advantage as hand-holes. Hand-holes can be set to any angle, and by thus frequent blasting yield greater tonnage per foot of hole. ”

“ The large charges in deep holes break the walls very irregularly; misfires cause more delay; timbering is more difficult in the face of heavy blasting charges; and the larger amount of spoil broken at one time delays renewed drilling, and altogether the advantages seem to lie with hand-drilling in shafts of large horizontal section.
The rapid development of special drills for particular conditions has eliminated the advantage of hand-work in many situations during the past ten years, and the invention of the hammer type of drill bids fair to render hand-drilling a thing of the past. ”

“ In recent years rotary drilling has been widely used in sinking deep oil wells. Boring is done by rotation of a bit attached to a steel pipe which when so used is called a 'drill stem.' A smaller bore, called 'rat-hole', sometimes precedes, and is reamed out to obtain, the full size hole. To aid operation, drilling fluid (mud-laden water) is pumped into the upper end of the drill stem and escapes into the well at high velocity through holes in the bit. ”

“ A drill support that occupies a large proportion of the free space in a shaft or a heading is thus a cause of inconvenience and a source of serious delay. Moreover, as it has to be continually removed from one situation to another, it should be of sufficiently light weight to allow of its being lifted or run along without difficulty. In underground workings, manual power is generally the only power available, and therefore it is desirable that both the machine and its support should be of such weight that each may be lifted by one man. ”

“ The weight and consequent mobility of a drill, aside from labor questions, have a marked effect on costs, for the lighter the drill the less difficulty and delay in erection, and consequent less loss of time and less tendency to drill holes from one radius, regardless of pointing to take best advantage of breaking planes. Moreover, smaller diameter and shorter holes consume less explosives per foot advanced or per ton broken. ”

“ It is the essence of speed in drilling, for, unlike the necessary principles to be adopted in the percussion methods of drilling, the rotary drill does not have to be lifted from the hole for the purposes of clearing. The pulverized strata are continuously washed from the hole by a stream of water reaching the bottom of the drill. Very frequently, a pressure-fed mud is used, and this serves a double purpose, for in its return to the surface it tends to plaster the walls of the well. ”

“ The deeper holes are made only in surface excavation of rock, the shallower, to a maximum depth of say 12 ft., being suitable for tunnelling and mining operations.
Hand Drilling.—The work is either “single-hand” or “double-hand.” In single-hand drilling, the miner wields the hammer with one hand, and with the other holds the drill or “bit,” rotating it slightly after every blow in order to keep the hole round and prevent the drill from sticking fast; in double-hand work, one man strikes, while the other holds and rotates the drill. ”

“ It sometimes becomes convenient in the exigencies which occur in the work of a general machine shop to hold a drill in a dog or clamp and feed it into the work with the lathe dead centre. In this case the drill should be held very firmly against the dead centre, or otherwise the drill may, when emerging through the back of the hole, feed itself forward, slipping off the dead centre, and causing the drill to catch and break, or moving the work in the chuck, to avoid which the drill should have a deep and well countersunk centre. ”

“ A more efficient method of hand-drill work is, however, where one man holds the drill, and another swings the hammer or sledge. Another form of hand drill, called a churn drill, consists of a long, heavy bar of steel, which is alternately raised and dropped by the workman, thus cutting a hole by repeated impacts. ”

“ Heavier machines are available for drilling larger and deeper holes. The same machine can be adapted to the use of steam or compressed air. When in use the point of the drill is placed against the rock and a pressure on the 265handle opens a valve admitting air or steam. The piston is caused to reciprocate in the cylinder, striking the head of the drill at each stroke. The drill is revolved in the hole by hand or by a mechanism in the machine. A hollow drill can be used by means of which the operator admits air or steam to the hole, thus blowing it out and keeping it clean. ”

“ The drill must be tried for running true at each end of the cylindrical body of the drill, which, being true with the square shank, may be taken as the standard of truth in grinding the drill, so that supposing the hole in the driving spindle to be true and the drill shank to be properly fitted, the drill will run true whichever way inserted. If the body of the drill runs out of true it will cause a great deal of friction by rubbing and forcing the cuttings against the sides of holes, especially if the clearance be small or the hole a deep one. ”

“ Most drills are made on the twist pattern, and it is something of a trick to grind a twist drill, but anyone can do it if he tackles the job with a determination to do it right. In grinding a twist drill, use a new drill for pattern. Grind the angles the same as the new drill, and be careful to have the point in the center. A little practice will make perfect.
Mechanics will say that no one except an expert should attempt to grind a twist drill, but farmers who are mechanically inclined are the best experts within reach. It is up to a farmer to grind his own drills or use them dull. ”

“ By their use many great tunnels and other works involving rock excavation under adverse conditions have been rapidly and successfully carried out. Before the invention of machine drills such work progressed slowly and with difficulty. Nearly all machine drills are of the reciprocating or percussive type, in which the drill bit is firmly clamped to the piston rod and delivers a rapid succession of strong blows on the bottom of the hole. ”

“ He operated on a piece of hard diorite an inch and three-eighths in thickness, and employed as a drilling agent a wooden wand of ash, or at times, of pine, in conjunction with sharp quartz sand. Attached to the wand was a heavy disc, to act as a fly-wheel, and an alternating rotatory motion was obtained by means of a bow and cord attached at its centre to the apex of the drilling-stock, and giving motion to it after the manner of a "pump-drill," such as is used by the Dacotahs [100] and Iroquois [101] for producing fire by friction, or what is sometimes called the Chinese drill. ”

“ According to the specification, the invention consists in the arrangement and application of a support-piece to the slide-rod, together with the drill-shaft, and the operating mechanism of such shaft, by the employment of which the patentee is enabled to support not only the vibrating lever of the pawl, but other parts of the drilling apparatus, and particularly to employ a driving-shaft and certain gears for the purpose of increasing the speed of the drill-shaft. ”

“ In using small drills in a machine it is of the first importance that the amount of pressure necessary to feed the drill be plainly perceptible at the hand lever or other device for feeding the drill or the work, as the case may be, as any undue pressure causes the drills to break. To attain sensitiveness in this respect the parts must be light and easy both to move and to operate.
Fig. 1671 represents the American Tool Company’s delicate drilling machine for holes of 1⁄4 inch and less in diameter. ”

“ The man who holds the drill raises it a little after each blow, and turns it [129] partly round, the degree of turn usually given being about one-eighth of a revolution. By this means, the hole is kept circular, and the cutting edge of the drill is prevented from falling twice in the same place. To keep the tool cool, and to convert the dust and chippings into sludge, the hole is kept partially filled with water, whenever it is inclined downwards. ”

“ Power Drilling.—In power drilling the drill is driven by a reciprocating machine which either strikes and turns the drill in the hole, or lifts and turns it as in churn drilling, or the drill may be driven by a rotary machine which is revolved by compressed air, steam, or electricity. ”

“ When an auger takes its way through a plank it removes as chips all the wood within the circle of its range; a drill, of common form, as it pierces stone or metal acts in a similar manner. Motive power is greatly economized when a drill is tubular, with the further advantage that within the ring cut a solid cylinder remains to be broken off at intervals and lifted out, its core informing to the engineer in quest of bed-rock, to the prospector of mines or oil-fields, [92] or to the geologist who reads at a glance the composition of a mineral, the forces which have impressed it age after age. ”

“ There is also a sluice, or slider, which lies flat on the bottom, on the inside of the drill-box, and juts out between the two handles of the drill, so as to be within the reach of the person guiding it; who, by pushing the slide forwards, completely covers the notched roller, and prevents any of the seed from being scattered, while the drill is turning at the end of the ridges. With this implement, a woman, or boy, is able to drill from 2 to 2 1/2 acres in a day; the rows being at the distance of 20 inches. ”

“ It is capable of drilling locker shells of any diameter between four and eight feet. The feed motion to each drill is driven from one source of power, but each drill is adjustable on its own account. The depth of feed is regulated by a patent detent lever which engages with the teeth of a ratchet wheel, till released therefrom by contact with the adjustable stop. The drill spindle is then instantly forced back by the spiral spring and the forward feed motion continues. ”

“ It will be obvious from these considerations that the more correctly the drill is ground, the longer it will last without regrinding, the greater its amount of feed may be to take an equal depth of cut, and the nearer the diameter of the hole drilled to that of the drill—the most correct results being obtained when the drill will closely fit into the hole it has drilled and will not fall through of its own gravity, a result it is somewhat difficult to attain. ”

“ The ordinary rock drill is really a pneumatic hammer. The tool, which is chisel-shaped, is used as a hammer to pound a hole in the rock. The tool is driven up and down or in and out by compressed air bearing alternately on opposite sides of a piston. The elasticity of the compressed air acts as a cushion to relieve the machine from shock. The drill is mounted upon a tripod in such a way that it may be operated in any direction. ”

“ In cases of extreme hardness two drills may with advantage be used intermittently upon the same hole; one of these should have its cutting edges ground at a more acute angle one to the other than is the case with the other drill, thus the cutting edge will be lessened in length while the drill will retain the strength due to [I-445] its diameter, so that a maximum of pressure may be placed upon it. When one drill has cut deep enough to bring its full length of cutting edge into action, it may be removed and the other drill employed, and so on. ”

“ The rates of feed are proportioned to the kind of drilling to be done. When the back gear is not in use and small drills are to be driven, the range of feeds is through a finer series than when the back gear is being used, and large drills or boring bars are [I-431] to be driven.
Fig. 1679 represents a drilling machine of English design. The cone pulley a is provided with back gear b placed beneath it, the live spindle driving the drill spindle through the bevel gears c, one of which is fast upon a sleeve d through which the drill spindle e passes. ”

“ In the evening the drillers, with their powerful air-drills, bore a series of five or six six-foot 'shot-holes,' four along the roof, and two on each side for the 'rib-shots.' Then a third crew of men, the 'shot-firers,' fill the deep drill-hole with long cartridges of coarse black powder, and blast down the coal, which falls broken and crumbled into the cut prepared by the machine-men. ”