IADC code

Classification of roller cone bits by IADC (International Association of Drilling Contractors) code is based on fourdigit code which represents the bit design and type of rock formation the drill bit is suited for. The first three digits are numerals and the fourth one is a letter

IADC code


Hardness of rock formation

The first digit represents the hardness of rock formation the drill bits are suited for. Every drill bit is designed for a certain type of rock formation, ranked according to hardness. The tool is assigned a numeral between 1 and 8 indicating the type of rock the teeth or buttons of a drilling tool are designed for:

1, 2 and 3: Drill bits with milled steel teeth. 1 is engineered for soft rock formations, 2 for medium formations, and 3 for hard formations.

4, 5, 6, 7, and 8: Drill bits with tungsten carbide inserts (TCI). Within this category 4 is designated for the softer formations, with 8 representing the hardest formations.


Further formation properties

The second digit represents further properties of drillable formation. Regardless of tooth/insert type, the second digit takes into account all factors of the bit and ranks the rock formations the drilling tool is best suited for on a scale from 1 to 4. 1 represents soft formations going up to 4 representing the hardest formations.


Type of bearings

The third digit represents the bearing type of the drilling tool.

Special features

The fourth digit is a letter indicating the special features of the drilling tool. In addition to the buttons, intended rock formations, and bearings used, tricone bits can have numerous other special properties:

  • 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 inserts shape

IADC code example


a drill bit with steel milled teeth for medium-soft rock formations (21), with sealed rolling-element bearings (4), with extended jets (E).


a drill bit with tungsten carbide inserts for mediumhard rock formations (63), with open air-cooled bearings (2), with conical inserts (Y).