STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Drilling Bits and Downhole Tools 809
WITH ISTEEL OTHER NATURAL BOW -0350-~::~
OIAUONO
IYPRE ONATE0
CUTTER1
/\
LONQ TAPER
PROF 1LE
R I&EO
WITH
FIXE0
PORTS
OIAMONO
Figure 4-164. Example of steel body impregnated core bit with face
discharge flow [54]. (Courtesy SPE.)
port, ribbed design. Finally, the number 0 is used for impregnated natural
diamond bits. Therefore the complete IADC classification code for this fixed
cutter bit is 0 3 5 0. Although the classification code for this bit does not
explicitly indicate the cutter type and body material, it can be inferred from
the rest of the code that this is an impregnated natural diamond, nonmatrix
body bit, in which case steel is the most likely body material.
Dull Grading for Fixed Cutter Bits
The section describes the first IADC standardized system for dull grading
natural diamond, PDC, and TSP (thermally stable polycrystalline diamond) bits,
otherwise known as fixed cutter bits [55]. The new system is consistent with
the recently revised dull grading system for roller bits. It describes the condition
of the cutting structure, the primary (with location) and secondary dull
characteristics, the gage condition, and the reason the bit was pulled.
The format of the dull grading system is shown in Figure 4-165. For completeness,
Figure 4-165 contains all of the codes needed to dull grade fixed cutter
bits and roller bits. Those codes which apply to fixed cutter bits are in boldface.
Eight factors about a worn fixed cutter bit can be recorded. The first four
spaces are used to describe the cutting structure. In the first two spaces, the
amount of cutting structure wear is recorded using the linear scale 0 to 8, based
on the initial useable cutter height. This is consistent with grading tooth wear