A drill bit assembly for a reverse circulation down-the-hole hammer includes a percussion bit having a head portion with a cutting face at a forward end thereof with engagement means on the head portion for engagement with complementary engagement means on a drive chuck whereby rotational drive from the drive chuck may be transmitted to the percussion bit. Connection means are provided on the drive chuck adapted for connecting the drive chuck to a drive means of the down-the-hole hammer. The percussion bit includes a central bore in fluid communication with the cutting face of the bit for returning a sample of drilled cuttings to the surface, a first plurality of flushing grooves in an outer surface of the head portion, and a second plurality of flushing grooves in an outer surface of the head portion.

A drill bit assembly for a reverse circulation down-the-hole hammer includes a percussion bit having a head portion with a cutting face at a forward end thereof with engagement means on the head portion for engagement with complementary engagement means on a drive chuck whereby rotational drive from the drive chuck may be transmitted to the percussion bit. Connection means are provided on the drive chuck adapted for connecting the drive chuck to a drive means of the down-the-hole hammer. The percussion bit includes a central bore in fluid communication with the cutting face of the bit for returning a sample of drilled cuttings to the surface, a first plurality of flushing grooves in an outer surface of the head portion, and a second plurality of flushing grooves in an outer surface of the head portion.

A downhole tool includes a body having a longitudinal axis and a fluid passage extending through the body. The downhole tool includes at least one blade having one or more engagement faces thereon. At least one junk slot extends adjacent to the at least one blade. The downhole tool includes a cleaning element at the longitudinal axis of the body. The cleaning element has a substrate bore in fluid communication with the fluid passage. The cleaning element includes at least one opening or passing a fluid from the substrate bore and out of the downhole tool through the at least one junk slot. A flow direction of the at least one opening is offset from the longitudinal axis.

A downhole tool includes a body having a longitudinal axis and a fluid passage extending through the body. The downhole tool includes at least one blade having one or more engagement faces thereon. At least one junk slot extends adjacent to the at least one blade. The downhole tool includes a cleaning element at the longitudinal axis of the body. The cleaning element has a substrate bore in fluid communication with the fluid passage. The cleaning element includes at least one opening or passing a fluid from the substrate bore and out of the downhole tool through the at least one junk slot. A flow direction of the at least one opening is offset from the longitudinal axis.

A hydrojet rotary drill bit (10) is provided for drilling a hole in a subsurface formation. The bit body (12) includes a plurality of axially extending ribs (16a, b, c, d, e, and f) and a flow channel between adjacent ribs. A plurality of cutting elements are fixedly mounting on a respective one of the plurality of ribs. A plurality of flow nozzles (20a, b, c, d, e, and f) made on respective one of the plurality of ribs to direct fluid (mud) to a respective one of the plurality of cutting elements to clean and cool the cutting elements.

A downhole tool includes a body having a longitudinal axis and a fluid passage extending through the body. The downhole tool includes at least one blade having one or more engagement faces thereon. At least one junk slot extends adjacent to the at least one blade. The downhole tool includes a cleaning element at the longitudinal axis of the body. The cleaning element has a substrate bore in fluid communication with the fluid passage. The cleaning element includes at least one opening or passing a fluid from the substrate bore and out of the downhole tool through the at least one junk slot. A flow direction of the at least one opening is offset from the longitudinal axis.

A downhole tool includes a body having a longitudinal axis and a fluid passage extending through the body. The downhole tool includes at least one blade having one or more engagement faces thereon. At least one junk slot extends adjacent to the at least one blade. The downhole tool includes a cleaning element at the longitudinal axis of the body. The cleaning element has a substrate bore in fluid communication with the fluid passage. The cleaning element includes at least one opening or passing a fluid from the substrate bore and out of the downhole tool through the at least one junk slot. A flow direction of the at least one opening is offset from the longitudinal axis.

A method for drilling with a drill bit includes communicating a fluid from a bottom hole assembly to a center of the bit; directing the fluid through at least one peripheral port or nozzle whose axis does not intersect with a surface of a bore of the drill bit; distributing the fluid through ports or nozzles coupled to a plurality of blades and junk slot areas distributed circumferentially around a center axis; and directing fluid with a plurality of ports or nozzles to the cutting elements for cleaning and cooling.

A method for drilling with a drill bit includes communicating a fluid from a bottom hole assembly to a center of the bit; directing the fluid through at least one peripheral port or nozzle whose axis does not intersect with a surface of a bore of the drill bit; distributing the fluid through ports or nozzles coupled to a plurality of blades and junk slot areas distributed circumferentially around a center axis; and directing fluid with a plurality of ports or nozzles to the cutting elements for cleaning and cooling.