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 following is an example of standard roller cone nomenclature:

The first digit actually denotes two different things:(1) Tooth or button
(2) Hardness of formation the tooth or button bit was designed to drillThe 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 are tungsten carbide inserts designed for different hardness with 4 being softest and 8 being the hardest.

The second digit indicates formation hardness the bit was designed to drill.
The number 1 is the softest formation and 4 the hardest.

The third digit indicates bearing type. For a more in-depth discussion of bearing types, click here. 

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



Compressive Strength

Very Low Strength

Low Strength

Medium Strength

High Strength

Very High Strength







An eight point dull grading system has been established by the IADC to enable drillers and bit manufacturers evaluate the performance of a drill bit. This eight point system is described below and is used on both tricones and fixed cutter bits: 

1. Inner Cutting Structure - Inner cutting structure wear is also noted by a number ranging from 0 to 8 with 0 being no wear and 8 being total wear.

2. Outer Cutting Structure - Outer cutting structure wear is also denoted by a number ranging from 0 to 8 with 0 being no wear and 8 being total wear.

3. Dull Characteristics - Dull characteristics enables the bit salesperson or driller to determine the overall, distinctive aspect of the dulled drill bit according to IADC standards as follows:

4. Location - Location describes where the damage is on the cone. N - Nose Row; M - Middle Row; G - Gauge Row; A - All Rows


Cone Number One contains the centermost cutting component. Cones two and three follow in a clockwise manner.

Nose row is the centermost cutting structure.

Gauge row is the outer most cutting structure.

5. Bearings/Seals - For open or roller bearing bits, bearing life is estimated on a scale of 0 to 8. Zero equals complete bearing intact, eight equals no bearing life left. "X" indicates fixed cutter.

If the drill bit has a sealed bearing, an "E" indicates the seals are effective or "F" is used to indicate failed seals.

For more information on tricone bearing types, click here.

6. Gauge - Gauge measures the amount of gauge wear a drill bit has suffered. 1=1/16" out of gauge; 2=1/8" out of gauge; 4=1/4" out of gauge.

7. Other Dull Characteristics - Any other dull grading characteristics should be noted here using the codes from #3.

8. Reason Pulled - The following codes are used to indicate the reason a bit was pulled from the hole:

BC - Broken Cone

BU - Balled Up

CD - Cone Drag

CR - Cored

ER - Erosion

HC - Heat Checking

LC - Lost Cone

LT - Lost Teeth

NR - Not Rerunnable

PB - Pinched Bit

RG - Rounded Gauge

SD - Shirttail Damage

TR - Tracking

WT - Worn Teeth

BT - Broken Teeth

CC - Cracked Cone

CI - Cone Interference

CT - Chipped Teeth

FC - Flat Crested Wear

JD - Junk Damage

LN - Lost Nozzle

NO - No Dull Characteristics

OC - Off Center Wear

PN - Plugged Nozzle

RR - Rerunnable

SS - Self Sharpening Wear

WO - Washed Out

BHA - Change Bottom Hole Assembly

CP - Core Point

DP - Drill Plug

DST - Drill String Test

DST - Drill String Test

HR - Hours on Bit

LOG - Run Logs

PR - Penetration Rate

TD - Total Depth/Casing Point

TW - Twist Off

WO - Washout

CM - Condition Mud

DMF - Downhole Motor Failure

DSF - Drill String Failure

DTF - Downhole Tool Failure

HP - Hole Problems

LIH - Left in Hole

PP - Pump Pressure

PP - Pump Pressure

TQ - Torque

RIG - Rig Repair

WC - Weather Conditions

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 for Tricones to Types of Drill Bits

Return to Atlas Copco

Share this page:
Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.