Various tools and machinery components useful for percussion drilling by hand
Chisels or Bits – The form, sharpness, and temper of the cutting tool employed vary according to the rock which has to be cut through. Various chisels are in use: flat or straight-edged for ordinary strata, V or diamond-pointed for hard rock; the T chisel for gravel, while others with a cutting edge like an S or Z are used for different kinds of work, but these chisels are difficult to sharpen and maintain in good order. For soft ground such as peat, augers are used. The chisels are 18 inches to 24 inches long, 1 inch to 2 inches in diameter, and 2 to 3 or 4 inches in breadth of face. They are made of the best steel, and weigh from 3 to 4 ½ pounds each. Figure 6 shows some of the forms used.
Rods. – The rods are made of wood or iron, more commonly the latter, the best materials being selected. They are octagonal, round, or square in section. Ordinary rods are ¾ inch to 1 ½ inches square, 7/8 inches and 1 inches; they are made in lengths of 1 ½ feet to 10 or 12 feet; the bottom rod is always about 3 feet long. The usual mode of connecting the rods is by a screw joint (Figure 7). Iron rods 1 inch square weight about 10 pounds per yard. Wooden rods are generally made in 20 to 30 foot lengths of pitch pine, and not less than 2 ½ inches square. The sections are joined by ordinary butt, or scarf, joints and iron strapping plates.
Bracehead. – For shallow holes boring can be accomplished by the single bracehead, actuated by two or more men, for a distance of 10 or 15 yards; beyond that depth a double bracehead is used until 20 or 30 yards is reached, when a spring pole and windlass will be required. The single bracehead is made with a wooden handle about 3 feet long and 3 inches in diameter at the center, and tapers at each end. The center is furnished with an eye made of iron to which the rods are attached (Figure 8).
Sludger.- The sludger is usually a tube 3 to 10 feet in length, and of a diameter suitable for the bore hole. It is provided with an ordinary clack or ball valve at the bottom (Figure 9). When it is required to clear the borehole, the sludger is lowered and worked up and down a few times at the bottom is order to fill it with the broken material; it is then drawn to the surface and the contents are carefully examined.
The Beche (horn socket) is the tool used for extracting broken rods in cases of fracture. it is about 2 feet long, and hollow for about 16 inches at the lower end, the diameter of the opening at the bottom being about 1 ¾ inches and tapering to 5/8 inches in diameter (Figure 10). This type of fishing tool is also known as a “horn socket”.
The Brake Staff is a lever of pitch pine 10 to 14 feet long having a fulcrum 1 ½ to 2 feet from the end next to the rods. At one end is placed an iron hook, a rope being attached to it to enable the men to give it motion (Figure 12). The brake staff serves the same purpose as a walking beam in operating the drilling tools during drilling operations.
An arrangement to guard against fracturing the [drilling] rods is the sliding joint [or “jars”] (Figure 13). The rods a a, below the joint, are made extra strong. When the chisel [drill bit] strikes the ground, the upper length of rods b move over the sliding joint until the beam to which it is fixed has completed its stroke. An elastic stop at the upper end of the sliding joint help deaden the fall, and thus the shock due to the chisel and rods striking the rock simultaneously is avoided.
If the rods happen to break, the ‘Bleche’, ‘Crow’s foot’ or some other grapnel is used to raise them. A simple kind of grapnel is a bell-mouthed tube about 5 feet long (Figure 14). Near the bottom of the inside of the tube are fixed four steel blades or springs. To extract the broken rods the tube is lowered until it passé over a joint below the fractured rod, the steel blades being pressed outwards when passing this joint, but immediately it is passed they press firmly in on the rod and the grapnel is then raised, taking the broken rods along with it.
Figure 11.- 1)spiral worm or miser 2)bell screw 3)bell box with cleats 4)crows-foot 5)bell-mouthed shell 6)auger shell 7)worm or auger screw 8)plug drill 9)parallel worm auger 10)shoe-nose shell 11)Auger-nose shell 12 & 13)shell augers 14)bow dog 15)spring dart 16)tillers or levers 17)gravel chisel 18)clay auger 19)reamer 20 & 21) lengthening pieces 22)lifting dog 23)nippling fork 24)hand dog 25)snatch block 26)auger cleaner 27)holding-up rod 28)tie spring driver 29)spring block
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