antiwhirl bit

1. n. [Drilling]
A drill bit, usually polycrystalline diamond compact bit (PDC) type, designed such that the individual cutting elements on the bit create a net imbalance force. This imbalance force pushes the bit against the side of the borehole, which in turn creates a stable rotating condition that resists backwards whirling, wobbling and downhole vibration. Antiwhirl bits allow faster rates of penetration, yet achieve longer bit life than more conventional bits, which are not dynamically biased to run smoothly, are inherently unstable, are vibration-prone and thus have shorter lives. No bit is whirl-proof, however.