Paper: Insert Rock Bits Reduce Drilling Cost

To gain a better understanding of the significance of insert rock bits in today's drilling, it is important to review the evolutionary process of the entire rock bit development. Modern-day rock bit technology began in 1909 with the introduction of the first rotary cone rock bit. Prior to this time, the use of the rotary drilling process had been limited to soft formations because harder formations were difficult or impossible to drill using the scraping action of the drag bit. The rotary cone bit, then, enabled the industry to drill much harder formations than previously possible. However, the early designs utilized cones which did not mesh. Consequently, the bit "balled" up" readily when drilling soft shale formations. In 1925, this problem was solved with the introduction of a two-cone bit with intermeshing teeth. As the teeth of one cone passed through the grooves of the opposite cone, accumulated formation was pushed from the grooves of the opposing cone; thus, it was called "self-cleaning." The new cutting structure enabled the drilling industry, for the first time, to make hole through both soft and hard formations with a single bit, markedly reducing overall time on each well. Until 1932, the basic bearing of rolling cutter bits remained the journal-type. Many attempts were made to effectively lubricate the bearing and extend bit life. However, none were effective, and bearing life remained extremely short until the introduction of anti-friction (roller) bearings in 1932.