This paper describes the development of a new range of Polycrystalline Diamond Compact (PDC) bits designed to have the smooth torque response of a roller cone bit but maintain the high penetration rates and long life achievable from a PDC bit. One such design features a 360 deg full contact gauge ring that prevents outer cutters from biting into the formation at gauge. This restriction to lateral movement reduces bit whirl and thereby increases cutting structure life. Thus because the bit drills more smoothly, torque fluctuations are lower resulting in a smoother bore hole which provides more predictable weight transfer. These advantages result in faster penetration rates when sliding because far less time is spent orienting the bit.
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