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Guidelines for safe and efficient roller cone bit operation
- Be careful when screwing the drill bit on and off to avoid damage.
- Avoid applying excessive pressure when screwing off or on.
- Ensure correct installation of unscrewing device, no foreign objects on platform.
- Clean threads of drilling rod and new bit, apply anti-seize compound.
- Perform coupling at low speed and low torque.
- Apply reduced load and speed according to “rule of thirds”:
➤ 2nd third → 2/3 of the recommended parameters.
➤ Final → regular parameters.
- After breaking-in, that cone temperatures are balanced.
- Purge cones to remove fitting grease.
- Maintain pressure differential ≥ 2.8 bar to protect the bearings.
- Ensure ascending stream speed:
≥ 2130 m/min for heavy cuttings.
- Indications of poor hole cleaning:
➤ Increased air feed pressure.
➤ Excessive cuttings at the hole bottom.
➤ Severe wear/damage to the bit legs.
- Always engage air feed before lowering the bit; keep it engaged until drilling completion.
- Rotate the bit when raising/lowering to clean cuttings and prevent ingress into bearings.
- In water-saturated formations or with water injection, maximize pressure differential.
- Prevent the bit from dropping to avoid damage to the bearings and weld seams.
- Check the backflow valve and ensure smooth cone rotation before installing a new bit.
- During long downtimes, manually rotate the cones to ensure they run freely.
- Periodically check air pressure and ensure there are no obstructions in rod or shackle.
- Inspect dull bits for foreign materials; log pressure values at each bit change.
- Inspect bit components for cracks, breakage, or bearing seizure.
- Avoid bent rods/components to prevent irregular loads.
- Apply sufficient but not excessive weight for effective rock chipping.
- Match rotation speed to rock type:
➤ High speed → higher ROP, but reduced penetration per rev and increased bit wear
- Never apply weight to the bit without rotation.
- Avoid drilling an already drilled hole section with a new bit.
- Clean used bits from cuttings.
- Examine wear pattern and log details.
- If large tungsten carbide chips appear → reduce speed/load.
- If erosive wear or cone top loss occurs with central blowing → switch to lateral blowing.
IADC Bit Classification
The IADC code (International Association of Drilling Contractors) is a four-character designation used worldwide to identify roller cone drill bits.
- The first three characters are numbers, the fourth is a letter.
- Together, they describe the bit’s design, formation, bearing type, and special features.
Digit 1 – Rock Hardness Category
Indicates the overall formation hardness the bit is designed for:
2 = medium formations
3 = hard formations
8 = extremely hard formations
- 1–3 → Steel Tooth bits
2 = medium formations
3 = hard formations
- 4–8 → Tungsten Carbide Insert (TCI) bits
8 = extremely hard formations
Digit 2 – Formation Detail (within hardness group)
Refines the application within the chosen hardness range.
It further classifies the formation from 1 (softest) to 4 (hardest) inside each category:
It further classifies the formation from 1 (softest) to 4 (hardest) inside each category:
- 1 = soft formations
- 2 = medium-soft
- 3 = medium-hard
- 4 = hard formations
Digit 3 – Bearing type
Defines the type of bearing system used in the bit:
- 1–3 → Open bearings
- 4–5 → Sealed roller bearings
- 6–7 → Sealed plain (journal) bearings
- 8–9 → Spare digits
Letter – Special features
The fourth character in the IADC code is a letter that identifies special design features of the bit.
A detailed explanation of the letter designations is provided below.
1 – Standard open bearing roller bit.
2 – Standard open bearing roller bit, air-cooled.
3 – Standard open bearing roller bit with gauge protection, which is defined as carbide inserts in the heel of the cone.
4 – Sealed roller bearing bit.
5 – Sealed roller bearing bit with gauge protection in the heel of the cone.
6 – Sealed plain bearing bit.
7 – Sealed plain bearing bit with gauge protection in the heel of the cone.
8, 9 – Spare digits.
2 – Standard open bearing roller bit, air-cooled.
3 – Standard open bearing roller bit with gauge protection, which is defined as carbide inserts in the heel of the cone.
4 – Sealed roller bearing bit.
5 – Sealed roller bearing bit with gauge protection in the heel of the cone.
6 – Sealed plain bearing bit.
7 – Sealed plain bearing bit with gauge protection in the heel of the cone.
8, 9 – Spare digits.
A – Air Application
B – Special Bearing
C – Center Jetted
D – Deviation Control
E – Extended Jets
G – Extra Gauge or Body Protection
H – Horizontal/Steering
J – Jet Deflection
L – Lug Pads
M – Motor Application
S – Standard Steel Tooth
T – Two Cone
W – Enhanced Cutting Structure
X – Chisel Inserts
Y – Conical Inserts
Z – Other insert shapes
B – Special Bearing
C – Center Jetted
D – Deviation Control
E – Extended Jets
G – Extra Gauge or Body Protection
H – Horizontal/Steering
J – Jet Deflection
L – Lug Pads
M – Motor Application
S – Standard Steel Tooth
T – Two Cone
W – Enhanced Cutting Structure
X – Chisel Inserts
Y – Conical Inserts
Z – Other insert shapes
Examples
- 214E → a drill bit with steel milled teeth for medium-soft rock formations (21), with sealed rolling-element bearings (4), with extended jets (E).
- 632Y → a drill bit with tungsten carbide inserts for medium-hard rock formations (63), with open air-cooled bearings (2), with conical inserts (Y).