While rock saws are a speciality, Toohey is one of the few manufacturers to have moved successfully into using diamond matrix cutting tools for harder rock. Tungsten carbide tools have been well proven in the Sydney sandstone, but different tools were required for hard rock as the saws started to gain a market in other areas.Toohey says the secret to getting a diamond matrix saw to work well is to match the diamonds to the rock, as different diamonds have different properties. However, the diamond matrix saw will cut a narrower slot, will be quieter and create less dust, and will be easier on the excavator when compared to a tungsten carbide blade.It is important to keep the diamonds cool during cutting, and a water spray system is fitted to the EAT saws. Toohey also builds them with a cover, so that mud spray is contained.Although he will build most types of attachment to order, most of Toohey’s attachments have some connection to cutting and handling rock. Apart from the saws, he makes forklift attachments to allow excavators to handle sawn blocks of stone, and swivel grabs that simplify the task of placing rocks when building a wall.Austeire Services specialises in rock cutting and has worked in the major tunnels in Sydney. Austeire now has three saws working in the cross-river tunnel in Brisbane. While tungsten carbide saws are generally best for Sydney sandstone, the harder Brisbane Tuff rock required a different type of saw, and diamond matrix saws built by Toohey and others are being used.Austeire owner Mark Haugh has a fleet of nearly 100 machines working on the east coast, including saws on excavators from 3t to 35t with a variety of boom configurations. He has saws made by a number of different manufacturers in his fleet.For the Brisbane tunnel job, he bought a new 22.5t zero tail swing excavator. Haugh says that meeting the demands of the major jobs requires a combination of good equipment, good operators, good maintenance and good safety standards.While rock saws have found a niche of cutting service trenches in tunnels, Haugh says the market does not fully understand the potential of these machines in a much wider range of excavation.Boundary saws allow rock to be cut vertically, right up to the perimeter of a basement excavation site. This precise cutting is faster than hammering and provides savings in the volumes of concrete or shotcrete used in perimeter walls.When trenches need to be cut in rock, making saw cuts on either side of the trench takes the tension out of the rock, allowing the material between the cuts to be removed readily with a hammer. Deep trenches can be excavated by making side cuts, removing the material between them, and repeating this until the required depth is reached, with the size of the hydraulic motor driving the saw being the limiting factor in how narrow the trench can be. If this work was done with a hammer, a tapered cut removing significantly more material would be required, as would more backfill material. Excavators of 45-50t or even larger can be required for hammer work, whereas a much smaller excavator can do the work with a saw. In very hard rock, even a hammer can struggle.The diamond matrix saw has broadened the range of conditions in which a rock saw can work. Haugh says: “The harder the rock, the better the diamond saw works.”
