Which bit type is typically used to drill through hard rock formations?

• A. Drag bit
• B. Diamond bit
• C. PDC bit
• D. Roller-cone bit

Answer: (C)

Hard rock drills need cutters that resist rapid wear and stay sharp under abrasion. A PDC bit uses fixed cutters with synthetic diamond material, giving exceptional wear resistance and a consistently sharp edge. Its simple, non-moving-cutters design also reduces the chance of mechanical failure in tough formations, allowing high penetration rates and longer bit life in hard, abrasive rock. Drag bits rely on scraping and don’t hold up well in hard rock, while roller-cone bits wear quickly on abrasive faces. Diamond bits can cut very hard rock too, but they’re expensive and brittle, making them less practical for routine hard‑rock drilling. So, for drilling through hard rock formations, the PDC bit is typically used.