NEARLY TON A YEAR

Evening Post, Volume CXXIII, Issue 18, 22 January 1937, Page 10

NEARLY TON A YEAR

DIAMONDS IN INDUSTRY MANY USEFUL PURPOSES (From "The Post's" Representative.) LONDON, January 2. Nearly a ton of diamonds, chiefly of inferior grades, is consumed industrially every year. Larger quantities, in fact, are used for industrial purposes than for personal adornment. The Bulletin of the Imperial Institute states that in recent years at least 60 per cent, by weight of the world's output has been of stones suitable only for industrial purposes. Whereas the gem diamond is mainly preserved, the industrial diamond is consumed.

In view of its hardness, the industrial diamond is chiefly used for abrasive purposes, mainly in the form of tools of various kinds, including the crowns of as well as in the form of just for lapping. The dust may also >e bonded and moulded into abrasive vheels. Diamonds are also employed 'or the reverse purpose, namely, to vithstand abrasion by other substances, lotably in the form of draw-plates or lies for wire-drawing, and as jejt for >il-burning furnaces. The majority consumed annually iprobably 40 per cent.) are used in the orm of diamond-tipped tools for tryng up abrasive wheels made of emery, :arborundum, etc., of which large lumbers are employed by engineerng firms for precision grinding. • Diamond-pointed tools are being used o an increasing extent for the accurate machining of many non-ferrous netals and alloys, as well as of elonite ind synthetic resins, such as. bakelite. n the motor manufacturing industry, or instance, they are used for the nachining of big-end bearings and iluminium alloy pistons. The durabilty of the points of these tools permits if much saving of time, as they enable •epetition work to be carried out for ong periods without re-setting the nachine. The technique of manufacure of diamond-set tools is rapidly idvancing. Diamond dies are widely used m vire-drawing, especially for very fine vire, and this use probably accounts 'or about 20 per cent, of the consump;ion. The cutting of building stones s quickly done with steel circular ;aws carrying diamonds around the Periphery. A large saw of this type, •ft in diameter, which would have nore than 1000 diamonds embedded n its edge, has a life of some 2500 sawng hours before the stones need reletting. A new and superior type of jutting or grinding wheel incorporating :rushed diamond is shortly to be manulactured commercially.

The Union of Sofith Africa has long been the principal producer of diamonds for gem purposes, but owing to the suspension of work at the mines the quantity of industrial diamonds produced there has been greatly reduced for several years past. On the other hand, the greatly-increased diamond output of the Belgian Congo, and Angola consists largely of stones unsuitable for jewellery and these countries provide most of the world's industrial diamonds. A proportion of the stones from West Africa and Borneo are also of industrial grade.