What are the two main configurations of tri-cone roller-cone bits?

• A. Tungsten carbide tip and ceramic insert
• B. Milled tooth and carbide insert
• C. Diamond insert and steel teeth
• D. Carbide insert and diamond insert

Answer: (B)

Tri-cone roller bits come in two primary configurations: milled-tooth bits and carbide-insert bits. In milled-tooth bits, the cutting edges are machined from steel, giving a tough, economical option that works well in softer, less abrasive formations—the teeth wear down gradually as you drill. In carbide-insert bits, hard tungsten carbide inserts are brazed onto the teeth, providing superior wear resistance in hard, abrasive rocks, which extends bit life but at a higher cost and with different failure modes to consider. The two main configurations reflect how the teeth achieve cutting and wear resistance, rather than using other materials like ceramics or diamonds.