Case Study | Why Do Drill Bit Alloy Teeth Fall Off Prematurely?
Recently, a mining client contacted us.
Client Feedback:
“The drill bit can still drill, but it doesn’t last its normal lifespan. The alloy teeth start falling off, causing a significant decrease in drilling speed.”
The drill bit used on-site was a 4-inch DTH bit, and the geological formation was high-strength granite.
The client believed the problem might be with the quality of the alloy teeth, but after inspecting the failed drill bit, we found that the issue wasn’t simply a matter of alloy quality.
Disassembly revealed that some alloy teeth hadn’t fractured severely, but had simply detached entirely from their sockets.
Further analysis identified three key reasons:
First, excessive drilling pressure.
To increase the drilling depth, operators maintained high axial pressure for extended periods, subjecting the alloy teeth to impact loads exceeding their design limits, leading to brazed layer fatigue.
Second, insufficient slag removal efficiency.
The crushing of granite produces a large amount of hard rock powder. If this powder isn’t removed promptly, the drill bit repeatedly impacts the rock powder, increasing the lateral stress on the alloy teeth.
Third, the drill bit structure was incompatible with the formation.
The rock in this mining area is hard and highly abrasive, requiring a tooth profile and layout design more suitable for high-impact conditions.
To address these issues, we advised the client:
✅ Adjust the drill pressure to avoid prolonged overloading of the alloy teeth;
✅ Increase the air supply to improve borehole cleanliness;
✅ Re-match impact-resistant alloy teeth according to the rock formation.
After these adjustments, the alloy tooth breakage problem was significantly reduced, and the drill bit life was improved.
As an engineer, I believe that alloy tooth breakage does not necessarily indicate poor drill bit quality. Often, it’s a reminder that an imbalance has not been achieved between drill bit design, rock conditions, and construction parameters.
A truly good drill bit not only breaks rock but, more importantly, ensures that each alloy tooth reaches its expected lifespan.
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