Full resolution (JPEG) - On this page / på denna sida - Second part - IX. Mining Industry and Metal Production - 1. The Iron Mines (together with information regarding other mines). By the late Prof. O. G. Nordenström - Technics of mining
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700 IX. MINING INDUSTRY AND METAL PRODUCTION OF SWEDEN.
In Sweden as in some other countries, diamond-drilling is also used for
exploring ore-deposits and in excavating galleries and shafts. For diamond-drilling
in other countries, it is customary to use large and rather complicated machines,
which give cores from 230 to 400 millimeters in diameter, and which can bore
holes 2,000 meters deep or more. In Sweden, such diamond-drilling machines
have been used only on a few occasions. On account of the great compactness
which is characteristic for not only our oreB but also their countries, it is,
furthermore, not at all necessary to use drilling-machines which give cores of such
large diameter as those just described. At our iron ore fields there have been
used since 1887 very simple, cheap, and easily transportable diamond-drilling
machines which bore holes the thickness of whose cores is not quite one tenth
of the smallest diameter given above.
All the borings with these machines have been done by Svenska
diamant-bergborrningsaktieholaget, and the total depth of the borings done by this company
since the aforesaid year (1887), in metal mines alone, amounts to about 50,000
meters. In 1900 alone, about 6,000 meters were bored. There are doubtless
few countries where explorations by means of diamond-drilling in mines, in
relation to the production of ore, are so extensive as here in Sweden. — The
boring-machines of the Company are run partly by hand and partly by petroleum or
electric motors. Especially of låte years, the latter kind of motors have come
more and more into use.
Boring tools and explosives. For breaking ground we use in Sweden
as in other countries, boring and blasting when the ore and its country are of a
compact nature.
The tools used in boring are both hammers and drills, which for more
than thirty years have been made entirely of steel (Bessemer, Uchatius, or Martin),
and as explosives only preparations of nitro-glycerine have been used for an
equally long time. Gunpowder is no longer used in mining. Everywhere in the
Swedish mines the boring tools are adapted so as to give the greatest possible
effect. In singlehanded drilling, which is now exclusively used, the weight of the
hammer generally varies between 3-s and 4-5 kilograms, and the average weight
of the drill is from \ * to l-7 kilograms.
Besides by adapting this ratio of weight, the working effect has also been
raised by using steel of suitable hardness for the drilling tools and by giving the
bit a shape suited to our kinds of röck and ore, which as a rule are hard. By
these means such advance has been made that it has been possible to use
hammers for drilling 1,500 up to 3,000 meters without their wear or loss in weight
amounting to more than 0’3 to 0’6 kilograms; and as to the drilling effect, it is
usual in underhand drilling to drill 250 to 375 millimeters per man and hour,
and sometimes up to 600 mm.
Besides hand-drilling, machine-drilling is also used, not however in stoping;
but in mines where filling is used, these machines are much in use, and give
advantageous results. Such mines are found at Norberg, Grängesberg, Åmmeberg,
Dannemora, Falun, Striberg, and Stripa, where drilling machines are used both
in overhand and cross-stoping, and in driving galleries.
Among the different kinds of compressed-air drilling machines used, Schram’s,
Ingersoll’s and Rand’s, and modifications of these, have been found to be the best,
and are therefore in general use.
Electric röck drilling machines of the Marvin type have also been used
in recent years.
In order to give an idea of the efficiency which is generally reached in
using compressed-air drilling machines, it may be mentioned that in overhand
working, which is the usual fillingmcthod, the amount of röck broken loose per
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