Most raise-boring applications begin with the drilling of a pilot hole. The general length of a pilot hole varies from 30-1,000m, with standard drill pipes of 1.5m length. The time and cost involved in pulling the pipes out from a deep pilot hole is significant, and the service life of pilot bits is therefore crucial when it comes to keeping down cost and time for any raise-boring project.
One of the main reasons for changing bits in the hole is gauge wear. Consequently, in order to extend the service life of the pilot bits, Sandvik said a lot of its development work on the new bit design has focused on improving gauge protection.
The new Sandvik RR880 premium pilot bits provide both durability and hole straightness and up to 35% longer bit life than its predecessor, substantially reducing the time and cost for changing tools, the manufacturer said.
Göran Strand, product line manager for Sandvik Mining, commented: “With the new Sandvik RR880 pilot bits, you can drill longer between bit changes. Fewer bit changes means shorter project times and increased profit at the end of the day.”