THE DIAMOND ROCK DRILL.

Westport Times, Volume VIII, Issue 1140, 9 January 1874, Page 2

THE DIAMOND ROCK DRILL.

From the report given by The Times of the proceedings at the congress of the Iron and Steel Institute, which was this year held at Liege, Belgium, the following is extracted:—Major Beaumont. M P., read a paper on rock boring machinery, in which he referred, in the first place, to the various operations carried on by the aid of this class of machines, which include test bore holes in prospecting for minerals, driving drifts, galleries, and tunnels, shaft sinking and subaqueous operations. He then explained the manner in which those operations were practically carried out by the diamond Rock Boring Company with the diamond drill, the patents for which they are working. The diamond drill is in principle quite distinct from any other system of boring rock, and works by rotation, without striking a blow. Its action is rather that of abrading than that of cutting, and the effect is produced by the sheer difference in hardness between the diamond and the rock it is operating upon. The diamonds are set in an annular steel ring, in which they are fastened by making holes, as nearly as possible of the same size as the stones to be set, in which the latter are buried. The projecting portion is not more than sufficient to allow the water to pass. The metal is drawn round the stone so as to close it on every side, and to give as large a bearing surface as possible to resist the tendency of the stone to be forced out. This crown of diamonds is attached to the end of the steel tube, and kept rotating by machinery against the rock at the rate of about two hundred and fifty revolutions a minute. Water is supplied through the hollow of the bar, whence it passes under the cutting face of the crown to the surface of tho hole between the side of the latter and the outside of the boring tubes. The diamonds are thereby kept cool, and the rubbish from the cutting is washed away. The crown has to be pressed forward with a force depending on the nature of the rock to be cut, which varies from 4001b to 8001b. The cutting is done at speeds ranging from 2in to 4in per minute. The diamond rock drill has been extensively used in various engineering operations, both in this and other countries, with the most successful results. Iu a brief discussion which followed the reading of Major Beaumont's paper, it was contended that the diamond drill was of the greatest value in hard rocks, while for soft kinds it did not answer so well. To this conclusion Major Beaumont assented in his reply, observing that in sofc rock the diamond drill would not compare with haud boring ; in ordinary rock it would do five times as much as could be effected by hand, while in very hard rock, it wouid do six tiines as much.