To deal with problems when drilling in abrasive rock conditions, global supplier of equipment and tools, service and technical solutions for industry Sandvik introduced a “ground-breaking” new design for drill bits.

The primary applications for the top-centre drill bits include face drilling and bolting in mining and tunnelling environments, where long bit life is essential to cutting costs and improving productivity, the company notes.

A key priority when developing the new top-centre drill bit was to increase service life.

The Sandvik top-centre drill bits incorporate a significant upgrade to drilling bits, which are now available as standard products in bit sizes of 43 mm, 45 mm and 48 mm, with two to three raised-end buttons and seven to eight gauge buttons in grade GC80 and connections R32, Sandvik Alpha 330 and R35.

The value addition to mining operations from the top-centre drill bits include up to 80% longer grinding intervals and up to 60% longer bit life. Advantages for drill operators include higher productivity, as a result of a longer service life, and a safer work environment, as a result of fewer bit changes, while spending less time near an unreinforced face.

“The new bit design essentially delivers more drill meters per shift, compared with a standard bit, owing to frequent bit changes,” Sandvik Mining Top Hammer Tools product manager Robert Grandin says.

The main reason for discarding a drill bit is excessive wear on the diameter. While the simplest way to achieve longer service life is to add more gauge buttons, this can be problematic, owing to the limited space available.

Further, an increase in the number or size of the carbide buttons generally decreases the penetration rate: the same impact force yields a lower net force per button.

However, the new design incorporates a raised front, elevating two or three front buttons – depending on diameter size – a few millimetres above the gauge buttons located on the periphery of the bit.

The front buttons are further set at a slight angle, relative to the symmetric axis of the bit. The raised front creates a slight 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 the GC80 innovative cemented carbide grade.