Drill string · Drilling
Drill Bit
The cutting tool at the bottom of the string that breaks the rock.
What it does
Roller cone bits have cones with teeth that roll on the bottom and crush the rock. PDC bits, also called fixed cutter bits, have no moving parts and shear the rock with synthetic diamond cutters. Fluid jets clear the chips off the bottom and up the annulus.
Basics
| Roller cone | Milled steel teeth or carbide inserts |
| PDC | Fixed synthetic diamond cutters, no moving parts |
| Action | Crushing (cones) or shearing (PDC) |
Common failures
- Worn cutters or teeth, rate of penetration drops
Troubleshooting
- Symptom
- Rate of penetration falls in the same formation
- Likely cause
- Worn bit
- What to check
- Trip for a new bit