IADC Classification System For PDC Drill Bits

The IADC classification system, developed by the International Association of Drilling Contractors has been the representative voice of drillers worldwide since 1940.

This system has enabled drillers worldwide to exchange information using standard nomenclature and dull grading methods for PDC drill bits and tricones.

This system is not as widely used for PDC drill bits as it is for tricones. The IADC system for tricones is used the world over. However, a knowledge of IADC classification for PDC drill bits is helpful.

PDC Drill Bits Nomenclature

Parts of a PDC Drill Bit

Nomenclature for PDC drill bits consists of one letter and three numbers. The letter indicates body type: M for matrix,S for steel, and D for diamond The next three numbers indicate the following:

1. Formation Type To Be Drilled

2. Cutting Structure

3. Bit Profile

For example: M241

2=Formation type this bit will drill,
4=Cutting Structure,
1=Bit Profile

Geological formation type to be drilled are classified in the following manner:

(1) or (2) Soft and soft sticky-Highly drillable formations such as clay, marl, gumbo and unconsolidated sands.

(3) Soft-medium-Low compressive strength sands, shales and anhydrites with hard layers intermixed.

(4) Medium-Moderate compressive strength sand, chalk, anhydrite and shale.

(6) Medium hard-Higher compressive strength with non or semi-sharp sand, shale, lime and anhydrite.

(7) Hard-High compressive strength with sharp layers of sand or siltstone.

(8) Extremely hard-Dense and sharp formations such as quartzite and volcanic rock.


Very soft (1) to medium (4) formation type pdc bits have one dominant size of PDC cutter. PDC cutting structure is denoted in the following way:

2 - this bit has mostly 19mm cutters

3 - this bit has mostly 13 mm cutters

4 - this bit has mostly 8 mm cutters

For example: M431

4=This bit will perform well in medium formations, 
3=Cutting Structure consists of primarily 13 mm pdc cutters,
1=Bit Profile

Formation types 6, 7 and 8 are somewhat different. These bits are designed for the harder, more difficult drilling. Their cutting structures are denoted as follows:

1 - Natural Diamond

2 - TSP (Thermally Stable Polycrystalline)

3 - Combination

4 - Impregnated Diamond


1 - Short Fishtail

2 - Short Profile

3 - Medium Profile

4 - Long Profile

For example: M612

4=This bit will perform well in medium hard formations, 
1=Cutting Structure consists of natural diamond,
2=Short Profile

Related Pages:

API Standards:  API standards, including pin sizes for drill bits and acceptable tolerances for rock bits and pdc bits.  

Atlas Copco:  Atlas Copco bit selection guide, examples of shirttail protection, and TCI and steel tooth cutting structure. 

Button Bits:  Button bits offer several advantages over PDC drill bits: they are less expensive and can withstand higher impact.

Drag Bits:  Drag Bits manufactured as one solid piece of alloy steel offer greater durability and reliability.  Available in step and chevron styles for hard rock drilling.

Dull Grading:  Dull grading drill bits is important but often overlooked.  This process provides valuable information for proper bit selection.

IADC:  The IADC classification system for tooth and button bits explained as well as dull grading codes and what they mean.

IADC Classification:  The IADC classification system for PDC bits:  pictures and explanation of what it means and how to use it.

PDC Cutters:  Because of PDC cutters, PDC bits drill sixty-five percent of total footage.  Their shearing action is more efficient than the crushing action of tricones.

PDC Drill Bits:  Available in either matrix or steel bodies, PDC drill bits  offer higher rate of penetration than tricones in many different formations.

Tricones:  With the exception of cutting structure, tricone bits are designed in the same manner regardless of manufacturer. 

Well Completion Bits:  Well completion drill bits from Atlas Copco in both tooth and button bits.  Bear Claw, Hurricane, Aardvark, and PDC diamond mill bits from KC Bit & Supply.

Return from IADC Classification to Types of Drill Bits

Return to Atlas Copco

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