IADC Classification System
Button Bits For Hard Rock Drilling
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 as the IADC system for tricones is used the world over. However, it’s helpful to have a knowledge of the IADC classification system for PDC drill bits.
PDC Drill Bits Nomenclature
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:
- Formation Type To Be Drilled
- Cutting Structure
- Bit Profile
For example: M241
M=Matrix
2=Formation type this bit will drill
4=Cutting Structure
1=Bit Profile
The classification of geological formation type the bit can drill is as follows:
(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.
PDC Cutting Structure
PDC cutting structure refers to both cutter size in millimeters as well as cutter type – natural diamond, TSP, combination, and impregnated diamond.
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:
1 – natural diamond in any size
2 – this bit has mostly 19mm TSP cutters
3 – this bit has mostly 13 mm combination cutters
4 – this bit has mostly 8 mm impregnated diamond cutters
For example: M431
M=Matrix
4=This bit will perform well in medium formations
3=Cutting Structure consists of primarily 13 mm pdc cutters
1=Bit Profile
Harder, more difficult drilling requires types 6, 7 and 8 with their cutting structures denoted as follows:
1 – Natural Diamond
2 – TSP (Thermally Stable Polycrystalline)
3 – Combination
4 – Impregnated Diamond
Bit Profile
1 – Short Fishtail
2 – Short Profile
3 – Medium Profile
4 – Long Profile
For example: M612
M=Matrix
4=This bit will perform well in medium hard formations,
1=Cutting Structure consists of natural diamond
2=Short Profile
IADC Classification Standards For Tooth and Button 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 of roller cone identification was established in 1987 and expanded in 1992 to include more features.
The first digit actually denotes two different things:
(1) Tooth or button
(2) Formation hardness the tooth or button bit can drill. The numbers 1, 2 and 3 indicate a tooth bit with 1 being used for soft formations, 2 for medium, and 3 for hard. The numbers 4, 5, 6, 7 and 8 denote tungsten carbide inserts designed for different formation hardness with 4 being softest and 8 being the hardest.
The second digit indicates formation hardness the bit can drill. The number 1 is the softest formation and 4 the hardest.
The third digit indicates bearing type. Click here for a more in-depth discussion of bearing types. The numbers 1, 2 and 3 indicate a roller bearing, 4 and 5 a sealed roller bearing, and 6 and 7 indicate a sealed journal bearing.
The fourth digit is a letter code indicating certain characteristics:
A – Air Application
B – Special Bearing
C – Center Jetted
D – Deviation Control
E – Extended Jets
G – Extra Gauge/Body Protection
H – Horizontal/Steering Application
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
Engineering Classification for Rock Hardness
Classification Compressive Strength
Very Low Strength <4000
Low Strength 4,000-8,000
Medium Strength 8,000-16,000
High Strength 16,000-32,000
Very High Strength >32,000
