Tool system creates synergy between 20kW rock drills and 45mm drill bits
A 30 to 80 per cent increase in rod life, more accurate collaring and straighter blast-holes are the main benefits of Alpha 330, a brand new tool system developed by Sandvik. Designed to exploit the power of 20kW drifters to drill small-diameter holes faster, Alpha 330 signals a new era of rock-tool economy.
Even an amateur knows it is no good using a big hammer to drive a small nail. The same principle applies in percussive rock-drilling, which is why manufacturers go to great lengths to match the strength of the drilling tools with the impact energy of the rock drill.
But what happens when market forces demand both a big hammer and a small nail?
The analogy reflects what has happened in drifting and tunnelling with cross-sections up to 50m2. In a nutshell, mining and civil engineers are keen to exploit the power and speed of 20kW rock drills in order to raise productivity, yet insist on keeping the bit diameter small – 45mm to be precise.
The snag is that the conventional R32 thread at the front of drifter rods for 45mm bits – nominally the biggest thread possible – is not quite man enough for the punishment meted out by 20kW machines, especially when the predominant rock resistance presents itself to the drill bit obliquely, causing the rod to bend.
Breakages occur typically at the gooseneck between the full rod-section and the R32 thread. With Alpha 330, which has a much more robust connection between the rod and bit, the frequency of such breakages is a thing of the past. The resultant tool economy, together with more accurate collaring and straighter holes that give better fragmentation and improved profile-control, brings down the overall cost of drifting and tunnelling yet again.
Even an amateur knows it is no good using a big hammer to drive a small nail. The same principle applies in percussive rock-drilling, which is why manufacturers go to great lengths to match the strength of the drilling tools with the impact energy of the rock drill.
But what happens when market forces demand both a big hammer and a small nail?
The analogy reflects what has happened in drifting and tunnelling with cross-sections up to 50m2. In a nutshell, mining and civil engineers are keen to exploit the power and speed of 20kW rock drills in order to raise productivity, yet insist on keeping the bit diameter small – 45mm to be precise.
The snag is that the conventional R32 thread at the front of drifter rods for 45mm bits – nominally the biggest thread possible – is not quite man enough for the punishment meted out by 20kW machines, especially when the predominant rock resistance presents itself to the drill bit obliquely, causing the rod to bend.
Breakages occur typically at the gooseneck between the full rod-section and the R32 thread. With Alpha 330, which has a much more robust connection between the rod and bit, the frequency of such breakages is a thing of the past. The resultant tool economy, together with more accurate collaring and straighter holes that give better fragmentation and improved profile-control, brings down the overall cost of drifting and tunnelling yet again.
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