... double-tube core drilling)1.Drill rod:BQ NQ HQ PQ 2.Core barrel: BQ NQ HQ ... Drill tool: hoisting plug water swivel overshot outer tube & inner tube wrench foot clamp etc5. P- Gauge Core ... , B116, B131, B14613. Chinese Standard Metric Core Bits for Single Tube Core Barrels: φ36, φ46, φ56, φ59, φ75 ... φ219, φ27514. Chinese Standard Metric Core Bits for Double Tube Core Barrels: φ56, φ59, φ75, φ9115. Chinese ...