DIAMOND SAWS

Sawing hard materials by means of diamond saws has become an important industry. At first, diamond saws were made by fastening individual diamonds round the rim of a wheel, or by forcing them into the edge of a long blade (gang-saw blade). There has of late been a considerable change in approach, and the majority of saws now made incorporate a thin layer of bonded diamond round the edge. A typical saw is shown schematically in which the bonded diamond region is shown shaded. Such wheels are made over an extremely wide range of sizes. Sizes of disc can vary from wheels a few inches across to wheels 8 feet in diameter! The large sizes can cost over £1500.

Diamond-bonded saws are used extensively in the building industry. Cement slabs can be cut to shape, porcelain, bricks, tiles, and so on, are easily shaped accurately also. The machines are now extensively used in connection with cutting stone for marble slabs for buildings or monuments, and especially for production of granite blocks. Large blocks are also reduced rapidly by the use of multiple blade-reciprocating saws. One advanced machine handles a cubic block of side about 10 feet, and has 40 blades cutting out blocks simultaneously. The saw blade edges themselves are about 1 inch wide, consisting of bonded diamond. Speed of cut is rapid and big blocks are quickly reduced.

Rotary saws have been found useful for making anti-skid ruts in concrete roads and aerodrome runways and have been brought to stone bridges and so on for cutting out sections on the spot to facilitate repair work. Check also diamond stud earrings.

A notable advance in speed of surfacing of roads and run-ways has resulted from the use of mobile saws and smoothing machines. These can rapidly traverse extensive stretches of motorway or aeroplane runways. Multiple blades are designed to cut long narrow ruts across a road, thereby producing an excellent anti-skid surface. The concrete surface is much too hard to be sawn by anything other than a diamond saw.

Diamond saws are extensively used in the furnace refractory industry, for materials such as heated alumina are very hard, and there is no other way of handling refractories. A high-speed rotary saw cuts very rapidly through a thick block of class and is therefore of considerable value as a time-saver in the optical glass industry. The blades have to travel fast, cutting edges needing to move at least at 100 feet per second. Adequate water flow on the blade during cutting is an essential. The type of bond and the grade of grit must be carefully adapted to each specific objective. A considerable number of difficult constructional problems have been solved by the use of diamond saws. One method uses a disc saw with corrugated i-edge, impregnated with diamond grit. This assists the water coolant flow, an essential part of diamond-sawing technique. Blades like this have found valuable application for rock cutting, glass cutting, shaping of abrasive material like asbestos hoard, and so on.

Diamond saws are used for facing bricks, surfacing stone slabs, and a host of other operations. Their use is not exactly strategic in that they are replaceable by other methods, but I they are enormously faster in functioning than old conventional techniques. The preparation of a big aerial runway with anti¬skid ruts would be an impossibly slow task without a high-speed rotary diamond saw.