Pilot Bits
Rotary pilot bits for the downward pilot hole that the reamer will later follow. Pilot accuracy is the whole job, so bit and stabilisation choice matter more than penetration rate.
Features
- The reamer follows the pilot hole exactly, so pilot deviation becomes shaft deviation with no chance to correct it.
- Bit and stabiliser arrangement are chosen for straightness first and penetration rate second.
- Pilot diameter is set by the stem that will carry the reamer, not chosen independently.
- Cutting structure follows rock strength in the same way as any rotary bit.
- Survey of the pilot hole before reaming begins is standard practice and should be budgeted for.
Specifications
| Figure | Typical range | Unit | Why it matters |
|---|---|---|---|
| Pilot bit diameter | 229 - 349 | mm | Has to suit the stem and the reamer's stinger. |
| Cutting structure | carbide insert / steel tooth | Matched to rock strength and abrasiveness. |