IADC Dull Grading

Cutting Structure
Inner Rows Outer Rows Dull Char. Location Bearings/Seals Gauge Other Dull Char. Reason Pulled
X

 

Inner Cutting Structure   X
     
Outer Cutting Structure   Gauge
A measure of lost, worn and/or broken cutting structure.
Linear Scale: 0-8
0 - No lost, worn and/or broken cutting structure
8 - All of cutting structure lost, worn and/or broken		   (Measure in fractions of an inch)
I - In Gauge
1 - 1/16" Out of Gauge
2 - 1/8" Out of Gauge
4 - 1/4" Out of Gauge
     
Dull Characteristics   Other Dull Characteristics
BF - Bond Failure   (Refer to column 3 codes)
BT - Broken Cutters    
BU - Balled Up   Reason Pulled or Run Terminated
CR - Cored   BHA - Change Bottomhole Assembly
CT - Chipped Cutters   CM - Condition Mud
DL - Delaminated Cutters   CP - Core Point
ER - Erosion   DMF - Downhole Motor Failure
HC - Heat Checking   DP - Drill Plug
JD - Junk Damage   DSF - Drill String Failure
LM - Lost Matrix   DST - Drill Stem Test
LN - Lost Nozzle   DTF - Downhole Tool Failure
LT - Lost Cutters   FM - Formation Change
NO - No Dull Characteristics   HP - Hole Problems
NR - Not Rerunnable   HR - Hours on Bit
PN - Plugged Nozzle/Flow Passage   LIH - Left in Hole
RO - Ring Out   LOG - Run Logs
RR - Rerunnable   PP - Pump Pressure
WO - Washed Out   PR - Penetration Rate
WT - Worn Cutters   RIG - Rig Repair
    TD - Total Depth/Casing Depth
Location   TQ - Torque
A - All Areas   TW - Twist Off
C - Cone   WC - Weather Conditions
G - Gauge   WO - Washout - Drill
N - Nose    
S - Shoulder    
T - Taper    

 

API Fixed Cutter Bit Tolerances
BIT SIZE
(IN.)		 FIXED CUTTER BIT
O.D. TOLERANCE (IN.)		  

FIXED CUTTER BITS - RING GAUGING

Any fixed cutter bit should be ring gauged prior to running in the hole. Stabilizers should also be calipered or gauged to verify they meet API-approved outside dimension tolerances as shown in the following table. Fixed cutter bits should not be larger than the nominal diameter.
6-3/4 and Smaller -0.015 to +0.00  
6-25/32 to 9 -0.020 to +0.00  
9-1/32 to 13-3/4 -0.030 to +0.00  
13-25/32 to 17-1/2 -0.045 to +0.00  
17-17/32 and Larger -0.063 to +0.00  
A “no go” gauge is used to ensure a bit is not smaller than allowed and, as the name implies, it should not go or slip down the entire length of the bit. A “go” gauge ensures a bit is not larger than allowed and should slip down the entire bit.