Improved Rock Drill.

Cromwell Argus, Volume V, Issue 214, 16 December 1873, Page 7

Improved Rock Drill.

The perfection of mechaiiic.il appliances to substitute hand-labour in the tedious and costly process bf rock-boring lias of late years occupied the attention of many ablo engineers, and a large variety of machines, more or less meritorious and successful, have been constructed and employed; The best known of this class—those designed and employed by Sommeillier in the construction of the Mont Cenis tunnel—were described and illustrated by us on a recent occasion. But although the Sommeillier drill reflects great credit on its designer, and although it performed invaluable work, it was complicated in its details, costly in. its repairs, and, compared to more recent apparatus for performing the same work, was imperfect in its action. Associated with the name of its designer, and the great undertaking carried through by its assistance, the Sommeillier rock-boring machine will be remembered with interest, rather than reproduced in practice, and it has already given place to others simpler in design, more rapid in action, aud less expensive to maintain. One of these, which has done good service in America upon the works of the Hoosac Tunnel, and which has since been brought into this country, is the Burleigh drill; but more lately a machine has been introduced which, by the simplicity of its details, and its rapidity in regular working, appears to surpass all that has yet been done in this direction. This is the M'Kean rock drill, which we illustrate this week, and shall proceed to describe. It is right to premise that the form of drill which is now being manufactured has been developed after a long experience, extending over several years, and lms gradually been perfected from a large number of experiments. So long ago as 18G6, Mr M'Kean turned his attention to the introduction of the Haupt boring machine to this country. This drill has been used to a considerable extent in America, especially upon the Hoosac Tunnel; but it fell far short of the necessary requirements, and, abandoning this arrangement, the inventor has succeeded in constructing a machine which, we think, will supersede any of the same class which has yet been introduced.

The great advantages possessed by the M'Kean drill are, that it consists of biit fewparts, all of winch are well designed for compactness and strength ; that it can be adjusted to any required position, so that holes can be drilled at any angle, the machine working with equal facility in every direction ; that its moving parts are only two, the piston and the pistpn rods with the cntter bar, and the valve ; that it is adapted to deliver from 500 to 1000 blows per minute, while the stroke of the piston and fall of the cutter bar is only 2hm. or 3in. ; that it is manipulated with the greatest ease, and that it is inexpensive. Moreover, as there is no shuck whatever upon any part of the machine except the cutter bar and piston, which is cushioned by the steam or air in the cylinder, the wear is reduced to a minimum. A minute description of the rock drill is then given, accompanied by drawings, and the description continues : In the foregoing description of the M'Kcan drill wo have alluded to it as being driven by steam ; this would, of course, be the case in all open work, and even in short headings, but compressed air would be required for tunnel work. In conclusion, we may add a few words upon the regular performance of the machines, one of which may be seen daily in operation at 42, Borough-road. This machine is of the size ordinarily used for quarry work or open cutting, weighing about loOlbs., with a single drill mounted on a frame. A smaller, and for many purposes a still more convenient form, is being manufactured, which can be handled by one man. With a steam pressure of 751bs. to the inch, it will drill, as a maximum, a 2] in. hole to a depth of 12in. per minute in Aberdeen granite ; but the average duty may be estimated at from Gin. to 9in. per minute, and the number of strokes from 500 to 1000. It is true some other machines have shown as high a duty as this, but none have hitherto been brought out which so completely fulfil all the varied requirements of a rock drill.— The Eivjinccrinrj.