Fixed cutter bits dull grading

The section describes the first lADC 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. 

Figure 4-165. I ADC bit dull grading codes—bold characters for fixed-cutter bits [55]. (Courtesy SPE.)...

The fifth space will always be an X for fixed cutter bits, since there are no bearings. This space can be used to distinguish dull grades for fixed cutter bits from dull grades for roller bits. 

Clark, D. A., et al., Application of the new lADC dull grading system for fixed cutter bits, SPE/IADC 1645, Proc. 1987 SPE/IADC Drilling Conference, New Orleans, March 15-18, 1987, pp. 851-858. 

---