THE MINER.

Cromwell Argus, Volume VI, Issue 290, 2 June 1875, Page 6

THE MINER.

THE DIAMOND ROCK-DRILL.

To some of our local mining companies now engaged in driving through hard country, the following description of the " Dia. mond Drill" and its boring capabilities, which we copy from the Melbourne Argus, will no doubt prove interesting and instructive : The diamond drill is in principle distinct from any other principle of holing rook, and works by rotation without striking a blow. Its action is rather that of abrading than cutting, and the effect is produced by the sheer difference of hardness between the diamond and the rock it is upon. Between the hardness of these there is no comparison. If a diamond be kept rotatiug against sandstone, it will cut a hole a mile deep before it was seriously worn. If of this resisting power proper advantage be taken, it follows that rocks can be holed without striking blows. This enables machinery of the simplest and most ordinary character to be used, and escapes the mechanical difficulty and risk of accident incidental to using powerful machinery in production of percussive action. And the gain increases in progressive ratio were the cutter is at a great distance (say in depth) from the source of power. The application of the diamond to rockdrilling is thus woi'ked out. The stones are set in an annular ring made of steel ; they are fastened in by making holes as nearly as possible the size of the diamonds to be set, and then burying them, leaving projecting only the amount necessary to allow the water and debris of the cutting to pass ; the metal is then drawn round the diamond, so as to close it on every side, and give as large a bearing surface as possible to resist the tendency of the stone to be forced out. The crown so set is attached to the end of a steel tube, and kept rotating against the rock at some 250 revolutions per minute. Water is supplied through the hollow of the bar, whence it passes under the cutting face of the crown to the surface of the hole between the side of the latter and the outside of the boring tubes ; the diamonds are there- j fore kept cool, and the debris from cutting washed away. The crown must be kept pressed forward with a force depending on the nature of the rock to be cut, varying from 4091b to 8001b, according to the rate of speed desired.

No rock is met in mining which approaches emerv in hardness. Yet a crown which had b-red through (actual experiment) 6ft of emery, 10ft of actual granite, and 95ft of hard sand-stone, was, so far as the diamonds were concerned, almost as fit for work as when new. The diamonds used are not valuable gems, but carbonate which until lately had no commercial value, and was first introduced for cutting other diamonds. The solid core, when formed, passes into a core-tube, and is kept from falling out on withdrawing the rods by means of sliding wedges or clips, which allow the core to pass freely np but prevent its returning. The great advantage claimed for this system of boring consists in the speed obtained, work being done in months that formerly took years, and in the precision of knowledge secured by the sample cores of strata.

The diamond rock-borer has survived the enoch of mere experiment. Early last year 30 machines were either at work or (some) preparing to commence. Here are a few actual results :—At Garrick, ironstone was reached »t 992 ft in 54 working days; at Moorsholme, 641 ft accomplished in 48 days; at Fishbonrne, coal reached at 434 ft in 54 days ; at Wollaton, 700 ft accomplished in 48 davs ; at Loftns, 640 ft occupied 60 days ; at Ballvmena, 558 ft in 42 davs ; at Chewton, 802 ft in 168 davs ; and at Beeston, 1008 ft occupied 146 days. Mr A. Brogden, M.P., in an interesting lecture (September, 1874) on the Rampside boring near Barrow, cites a bore at St. Rees 1467 ft deep, and one at Furness 1730 ft deep, completed in 14 months. Now, what a sum such an implement would have saved the Climes Consols Companv, the Newington, or the Magdala, at Pleasant Creek.

As an instance (says the Grey River Argus) of the important results which sometimes come from humble and insignificant beginnings the following literal transcript of what may be described as the original deed of association of one of the most celebrated of the extensive quartz-mining companies in the Inangahua district, will be read as a curiositv. The claim was at one time held by twelve shareholders whose interests were equal, and the document is an agreement that it is advisable to applvfor a gold-mining lease for the ground, and the contribution towards the expense of so doing is fixed for each shareholder : —" Angahoo Gooldfield. October 9th, 1871. Wee the Houlders off this Clame Do mak a kail of £2 at prisint to Put it intow a lace and tow Pounds mor in a month for tolls (tools?) and allso to Work it by tow min at prisent." Then follow the names of the shareholders, with the amount of the liability of each affixed. Although the " legal manager" has carried out bis peculiar stvle of orthography in spelling the names of his co-adventurer 3, still, anyone having had an acquaintance with the Inangahua at the time mentioned will recognise among the shareholders, notwithstanding the unintentional disguise in which they are made to appear, the names of several Gentlemen who have been associated with the rise and progress of the district, and who are now partij cipators in the prosperity the early pioneers I did so much towards bringing about.