This paper is one of two describing changes to the IADC Classification and Dull Grading Systems for fixed cutter bits. Dull grading system revisions, described herein, were implemented to improve utilization and effectiveness of the dull grading system. Classification system changes were required as a result of improvements in bit technology and applications, and are detailed in the companion paper SPE 23940.

Following extensive review of the existing system, development of a new IADC Fixed-Cutter Drill Bit Classification System was initiated in late 1990, based on input gathered from the industry concerning the change. It was determined that existing fixed-cutter bit classifications, which attempted to describe each bit style individually, were not being used. In contrast, the success of the roller cone bit classification system was believed to lie in its grouping of similar bit styles into categories, thus allowing users to relate familiar bit styles with unfamiliar ones. Specifically, the IADC Fixed-Cutter Work Group committee undertaking the task developed a fixed-cutter bit reference chart patterned after the existing roller cone classification table, which would allow bit styles to be grouped by similar type. IADC classification codes for each bit are then generated by placing the bit style on the chart in the category which best describes it, thus grouping similar bit types under a single category. The new classification system is composed of four characters, designating body material, cutter density, cutter size or type, and profile, respectively. It is presented as an attempt to improve the ability to classify and thus employ fixed-cutter PDC and diamond drill bits more effectively in the drilling industry.