The size of the cuttings is used as an indicator of bit condition. Which statement best describes this?

• A. Larger cuttings indicate bit wear
• B. Larger, uniform cuttings indicate efficient drilling
• C. Small cuttings indicate efficient drilling
• D. Cutting size has no relation to efficiency

Answer: (B)

Cutting size in air rotary drilling shows how well the bit is cutting rather than grinding. When the bit is sharp and operating efficiently, rock is fractured and broken into larger chips, and those chips tend to be uniform in size. That uniform, larger chip pattern means the bit is transferring energy effectively into the rock and the drilling is proceeding smoothly. If the bit is worn or damaged, it tends to grind the rock instead of cutting cleanly, producing many small or powdery cuttings and often uneven chip sizes. So seeing larger, uniform cuttings is a sign of good bit condition and efficient drilling.