US Patent 9428965 Subsurface drilling tool

An improved subsurface drilling tool comprises a shank having a cutting end opposite a pin end configured to attach to a drill string. A plurality of ear portions is associated with the proximate end of the shank and configured to form a socket. A ball-shaped cutting tool is configured to fit inside the socket and is rotatably attach to the ear portions via an axle. A locking pin may be installed within one or more of the ear portions and perpendicular to the axle. A plurality of blade inserts is connected to the ball-shaped cutting tool. The blade inserts may be removable and/or configurable to be oriented in varied directions. A series of milling courses may extend longitudinally along an outside length of the shank. A fluid course may extend longitudinally within the shank to deliver drilling fluid to the cutting end.