Fixed-Cutter Bits
Bits with polycrystalline diamond cutters and no moving parts, for soft to medium formations. Very high penetration rate where the ground suits them, and short life where it does not.
Features
- No bearings means no bearing failure, so life is governed by cutter wear and by impact damage.
- Penetration rates in soft and medium formations are substantially higher than a roller-cone bit at the same weight.
- Hard nodules, chert bands and broken ground chip the cutters, and a bit can be finished in a single run.
- Lower weight on bit is needed than for a roller-cone bit, which can suit a rig short on pull-down capacity.
- Cutter size and density are matched to formation: fewer large cutters for soft ground, more small cutters for harder ground.
Specifications
| Figure | Typical range | Unit | Why it matters |
|---|---|---|---|
| Bit diameter | 152 - 311 | mm | Set by the hole design and available pull-down. |
| Cutter size | 13 / 16 / 19 | mm | Larger cutters for soft ground, smaller for harder. |