Page 221 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 197

Drill Bit Selection, Parameters, and Hydraulics [ ]
2.4.6

The second code digit is type and it is a subclassification of hard-
ness. The code can be 1 to 4 for bits that increase hardness within the
formation hardness series.
The third code digit is feature classification and can be 1 to 9 as follows:

1 - Standard, nonsealed bearing
2 - Air lubricated, for air drilling
3 - Standard, nonsealed bearing with insert gauge protection
4 - Sealed roller bearing
5 - Sealed roller bearing with insert gauge protection
6 - Sealed journal bearing
7 - Sealed journal bearing with insert gauge protection
8 - Directional
9 - Special application

For example, a bit type IADC 5-4-7 could be a Hughes ATJ33, Reed
HP54, Smith F37, or Security S88F. Each of these bits has broadly com-
parable application as journal bearing insert bits for medium forma-
tions of high-compressive strength. Note that the bit manufacturer and
not the IADC gives a bit its IADC classification.
The system also defines 16 special codes that can be placed after
the IADC bit classification to show particular features.

IADC special feature code and description

A Air drilling application
L Lug pads
B Special bearing seal
M Motor application bit
C Center jet
S Standard steel tooth model
D Deviation control
T Two-cone bit
E Extended jet (full length)
W Enhanced cutting structure
G Additional gauge and body protection
X Predominantly chisel tooth inserts

197