INDUSTRIAL DIAMONDS

Lake Wakatip Mail, Issue 4011, 4 August 1931, Page 7

INDUSTRIAL DIAMONDS

EXTREMELY IMPORTANT INDUSTRY There is a quiet room, high up above the workaday traffic of London, which puts a spell on the stranger who enters it. Spacious, furnished in perfect taste, it has the atmosphere of the hall of a well-kept country mansion, aloof indeed from the customary bustle of business. You see little of impedimenta of ordinary commerce about it, but as you step across the softly-car-peted lloor your eye is caught by a long narrow table set under deep windows, and covered with dark hie felting on which are pinned sheets of white paper (says a writer in the supplement of the London ‘ Daily Telegraph ’ of April 27). At one of those clean-looking places a man sits, absorbed by a curious task. Between the finger and thumb of one hand he holds a tin}' weighing scale. A shiny, fascinating toy it looks. In one of the miniature pans there is a carat weight. Into the other the man puts a little lump of stone. There is a grey pile, hand-high, of these bits of stone before him on the white paper. They are diamonds, which he is examining and sizing.

The room is 'he centre of an extremely important industry It is part of the premises of Messrs L. M. Van Moppes and Sons, of Gardiner House, 10 Charterhouse street, E.C., 1, the well-known industrial diamond specialists, who hold the largest stock of industrial diamonds in the world. Tiie term “industrial diamond” implies nothing of synthetic manufacture or imitation. It is simply the name given to these diamonds which by reason of some deficiency of colour or constitution could not he cut and polished into ornamental gems at an economic cost. They are therefore employed for purposes of industry and science, where their unsurpassable qualities of hardness and refractive power make them invaluable. Some 40 per cent, of the weight, and from 15 to 20 per cent, of the x nine of all diamonds mim'd in an average year are put to those uses.

The hardness of the diamond is, of '-our.se, proverbial. It is the hardest SUbs Lance known. But the old phrase “Diamond cut diamond” has a literal as well as a metaphorical application. The commonest form of diamond known, though useless for specialised industrial work, comes into its own, romantically enough, a> a cutter and polisher of its precious jewel sister. Crushed to powder and mixe with olive oil, it is smeared upon a soft iron disc, turning at 2,500 revolutions a minute, whereon a diamond to be cut and polished is laid and weighted down, the wearing action .of the diamond dust eventually creating a gleaming facet upon it. The resistant and abrasive properties of diamonds arc turned to account in an enormous number of ways, llnough diamond drawplates or dies, all kinds of metal, from the tungsten filament of the electric lamp to the molybdenum, copper, lead, gold, and silver wires of science or the lame of brocaded and decorated fabric, can be drawn to a degree of fineness excelling that of human hair The very usefulness of telegraph and cable wire, tm example, is dependent upon rigid tin; formity of diameter. From one to two hundred tons of wire can be drawn through such a die without any variation of calibre or gauge and without any infraction of the diamond core of rhe die tisclf

Milling engineers find the diamond drill—a circulai tube, steel bit, nr rrown, set with diamonds projecting slightly above the surface--of inestimable service, since it cuts out a clean core, which can he brought it, the surface for determination of the precise nature and sequence of the strata through which a borehole is being driven Without the use of diamonds it is impossible to obtain a satisfactory sample core. These dribs can be taken to a depth ot over 4,000 ft and there is no known rock nr stratum which the diamond has failed to penetrate It is in precision grinding that the industrial diamond is supreme. The abrasive wheels used in grinding are themselves essentially hard, yet they are liable to wear down unevenly, and the mathematical accuracy of the work concerned is impaired in consequence. Moreover, the surface of the wheel periodically becomes glazed through impregnation with the powdered metal produced by the grinding, and to all intents and purposes ceases to grind. The diamond truing tool, with its keen cutting edge, shaves off the glaze, restores the truth of the circumferences, and leaves the wheel with a new and perfect surface. Such is the hardness of tiie diamond, and these arc only a few of the uses to which it is put. But apart hum the manufacture of drawing dies, which is almost exclusively a French industry, there is no phase of the industrial diamond industry in which the house of Van Moppes is not expertly equipped both in technique and experience.