STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

780 Drilling and Well Completions
Gauge Wear. When the bit pulled out of the hole is in gage, this is reported
by the letter "I." When the bit pulled out of the hole is out of gage, this is
reported by the amount of gage wear in + of an inch.
To measure the amount of gage wear on a used bit, set the ring gauge on
two cones and measure the distance between the ring gauge and the third cone
in fractions of an inch, or in millimeters.
Dull Grading of Roller Cone Bits. The grading is accomplished by using an
eight-column dull code as follows [46].
Cutting Structure 0 G Remarks
Inner Outer Dull Bring Gage Other Reason
Rows rows char. Location seal 7k dull pulled
(1) (0) (D) (L) (B) (GI (0) (R)
1. Column I (I) is used to report the condition of the cutting structure on
the inner two-thirds of the bit.
2. Column 2 (0) is used to report the condition of the cutting structure on
the outer one-third of the bit.
In columns 1 and 2 a linear scale from 0 to 8 is used to describe the
condition of the cutting structure as explained above.
For example: a bit missing half of the inserts on the inner two-thirds of
the bit due to loss or breakage with the remaining teeth on the inner twothirds
having a 50% reduction in height due to wear, should be graded a
6 in column 1. If the inserts on the outer one-third of the bit were all
intact but were reduced by wear to half of their original height, the proper
grade for column 2 would be 4.
3. Column 3 (D) uses a two-letter code to indicate the major dull characteristic
of the cutting structure. Table 4-92 lists the two-letter codes for the dull
characteristics to be used in this column.
BC - Broken cone
BT - Broken teethkutters
BU - Balled up
* CC - Cracked cone
* CD - Cone dragged
CI - Cone interference
CR Core
CT - Chipped teeth
ER Erosion
FC Flat crested wear
HC - Heat checking
JD Junk damage
LC - Lost cone
Table 4-92
Majorlother Dull Characteristics [46]
LN - Lost nozzle
LT - Lost teethkutters
OC - Off center wear
PB - Pinched bit
PN - Plugged nozzle
RG-Roundedgauge
RO - Ring out
SD - Shirttail damage
SS - Self sharpening wear
TR - Tracking
WO - Wash out on bit
'Show cone number(s) under LOCATION (L) column 4 of the IADC dull code.
Courtesy SPE
WT - Worn teeth/cutters
NO - No other majodother dull characteristic