Sandvik RT300 drill bits for big tophammers get tough new buttons that outlast all others in aggressive rock formations
Longer life, higher penetration rates and cleaner holes are among the benefits of a new generation of Sandvik GT60 button bits called RT300. Thanks to a new super-grade of cemented-carbide called XT48 and a new universal face design, their buttons are stronger and more wear resistant than ever while energy distribution and cuttings evacuation are enhanced. Superseding current versions, the new RT300 bits will reaffirm Sandvik GT60's position as the best tool system in the market for drilling big, straight, clean holes up to 33 m (110 ft) deep with fuel-efficient tophammer rigs.
High hardness and great toughness are two essential properties cemented-carbide buttons in drill-bits must have. Normally, however, they do not co-exist easily. The maxim is that if you make the buttons harder, they become more wear-resistant but too brittle. If you make them tougher, they become more elastic but less resistant to wear. In spite of this law, Sandvik has continually found new ways to make buttons both harder and tougher. The result has been continual improvements in both bit life and penetration rates, with ever-higher productivity and lower costs for customers. Combining this hard-materials technology with more effective cutting structures, greater rigidity and good flushing ports, Sandvik RT300/GT60 drills straight, clean holes 92-152 mm (3⅝-6 in) in diameter faster and more efficiently using only about half the fuel consumed by the DTH method.
XT48 – the grade that bends the rules
New Sandvik RT300/GT60 button bits have the suffix S48 (for spherical buttons) or R48 (for ballistic buttons) to indicate that they contain grade XT48 (= Extra Tough) cemented carbide. The hardest and toughest carbide ever made, it is a true multi-purpose hard-metal for rock bits that extends greatly the range of rock conditions in which any given Sandvik button bit can excel. Soon to be used in all other Sandvik button bits for benching and underground production-drilling as well, its secrets lie in new manufacturing techniques that give the cemented carbide a higher density and more homogenous structure than ever. In drifting and tunneling operations, where Sandvik has already introduced grade XT48 in drill-bits up to 51 mm in diameter, the results have been staggering. In extremely aggressive rocks that usually cause buttons to fracture prematurely, bit life has been almost doubled and productivity is up sharply as well. In the case of larger drill bits for benching, which have more body metal to support the buttons, the average increase in life will be 10-30 per cent depending on the rock conditions, together with a 5-10 per cent increase in productivity. What is more, every bit with grade XT48 carbide and the new universal face design (Uniface), which combines the best features of the former Flat Face and Drop-Center designs, is suitable for a much wider range of rock conditions. That means contractors can reduce their inventories and bring down drilling costs even further.
Spherical or ballistic buttons / regular or Retrac skirt
The first consideration when choosing a new Sandvik RT300/GT60 drill bit is whether to go for spherical or ballistic buttons. Put simply, spherical buttons (S48) are best in hard rocks while ballistic buttons (R48) drill faster in less- to medium-hard rocks. If ballistic buttons wear too fast, changing to spherical buttons will increase the service life. With regard to skirt design, a regular skirt is usually more economical in solid and homogenous rocks. In variable and fractured rock formations, however, from which it can sometimes be difficult to remove the drill string, a Retrac skirt is the answer. Sandvik Retrac bits, with their patented stepped-spline design, have excellent guidance in the hole and give superior straightness. When there are very high demands on hole-straightness in poor rock, placing one Sandvik GT60 pilot tube directly behind the drill bit assures optimum results.
For further information, please contact:
Sandvik Mining and Construction
Martin Lindfors, Marketing Communications
Phone: + 46 26 26 21 58