Capital Equipment News July 2016

MINING

Sandvik reinvents TOP HAMMER DRILL BIT DESIGN

​S olving a problem that a customer ex- perienced when drilling in abrasive rock conditions, has led to a ground- breaking new design for drill bits. The re- sulting Sandvik top centre drill bits, which incorporate the largest upgrades to face drilling bits in decades, are now available as standard products in three sizes. Primary applications for the top centre drill bits in- clude face drilling and bolting in mining and tunnelling environments where long bit life is essential for cutting costs and improving productivity. The top priority when developing the new top centre drill bit was to increase service life. Since the main reason for discarding a drill bit is excessive wear on the diameter, the simplest way to achieve longer service life is to add more gauge buttons. However, this can prove problematic because of the minimal space available. Furthermore, an increase in the number or size of the car- bide buttons generally decreases the pene- tration rate: the same impact force yields a lower net force per button. The new design solves these problems with a so-called raised front, elevating two or three front buttons – depending on diame- ter size – a few millimetres above the gauge buttons located on the periphery of the bit. Furthermore, the front buttons are set at a slight angle relative to the symmetric axis of the bit. The raised front creates a somewhat recessed hole bottom pattern that alters the rock-breaking action to achieve improved performance. In addition to the new design, the top centre bit also features a new, innovative cement- ed carbide grade, the GC80. “The problem with the carbides that exist on the market today is that they are either wear-resistant or tough,” says Robert Grandin, Product Manager Top Hammer Tools at Sandvik Min-

Sandvik top centre drill bits add value to operations:

For mine management Up to 80% longer grinding intervals Up to 60% longer bit life

For drill operators Higher productivity thanks to longer service life Safer work environment thanks to fewer bit changes

ing. “When developing the GC80, we want- ed to combine the best of those two worlds in order to get as much as possible out of the top centre design.” The key to this is a completely new pro- duction method, which makes it possible to produce a button that improves wear resistance on the outside, yet combines toughness with a softer centre, pushing the service life and long grinding intervals even further. Tool life improvements brought about by the Sandvik top centre design also yield signifi- cant health and safety benefits, since oper- ators spend less time near an unreinforced face. “The new bit design essentially deliv- ers more metres per shift compared with a standard bit thanks to less frequent bit changes,” Grandin says.

More than 1 000 hours of testing in wide- ly varying conditions and sites in countries including China, Turkey, Bulgaria, Georgia, Zimbabwe, Australia, Mexico and Sweden have shown operators logging more drilled metres and more holes between each re- grind. Less regrinding means less wear on the drill diameter. An additional benefit is more accurate collaring, which directly im- pacts the accuracy of drilled holes and con- sequently blasting results. “What started as a solution for an extreme customer problem is now a standard solution that can be used everywhere,” Grandin concludes. Top centre drill bits are available in bit sizes 43, 45 and 48 mm with 2–3 raised end but- tons and 7–8 gauge buttons in grade GC80 and connections R32, Sandvik Alpha 330 and R35. b