Abstract: A hammer bit includes a bit body having a bit axis and a bit face, a first circumferential row of cutting elements mounted to the bit face, the first circumferential row located at an outermost radius of the bit face and extending around the bit axis, and a second circumferential row of cutting elements mounted to the bit face, the second circumferential row located radially inwardly adjacent the first circumferential row, wherein each of the cutting elements of the second circumferential row is a semi-round top insert. The ratio of the radial overlap distance to the radial span distance between the cutting profiles of cutting elements of the first and second circumferential rows is between 0.1 and 0.5. The ratio of the radial overlap distance to the radial span distance between the cutting profiles of the first and second circumferential rows is greater than 0.25.

Abstract: A drill bit for use with a percussion drilling apparatus can include an elongated body with a first end, a second end, and a longitudinal surface extending between the first and second ends. A plurality of splines extends along the longitudinal surface of the drill bit internally, and at least one of the splines has an apex, a root, and a planar surface between the apex and root. The planar surface can be oriented at an angle to a plane extending from a center of the drill bit to a midpoint of the apex. The internal splines of the hammer bit correspond to external splines in a hammer casing.

Abstract: A hammer bit for drilling a borehole in earthen formations includes a bit body having a bit axis and a bit face, a plurality of gage cutter elements mounted to the bit face in a circumferential gage row, and a plurality of adjacent to gage cutter elements mounted to the bit face in a circumferential row that is radially adjacent the gage row. The ratio of the radial overlap distance to the radial span distance between radially overlapping gage cutter elements and adjacent to gage cutter elements is greater than 0.25. The ratio of the radial overlap distances to the diameter of the gage cutter element is greater than 0.25. An average cutting area of the gage cutter elements per gage cutter element is less than an average surface area of an entire cutting surface of each of the gage cutter elements.

Abstract: A hammer bit for drilling a borehole in earthen formations comprises a bit body having a bit axis and a bit face. The bit face includes an inner region extending from the bit axis to about 50% of the bit radius and an outer region extending from the inner region to the outermost radius. In addition, the bit comprises a plurality of gage cutter elements mounted to the bit face in a circumferential gage row in the outer region. Further, the bit comprises a plurality of adjacent to gage cutter elements mounted to the bit face in a circumferential adjacent to gage row in the outer region. The cutting profile of at least one cutter element in each row in the outer region radially overlaps with the cutting profile of at least one other cutter element in a different row in rotated profile view.

Abstract: A percussion drilling assembly for boring into the earth. In an embodiment, the assembly comprises a tubular case having a central axis, an upper end, and a lower end. In addition, the assembly comprises a piston slidingly disposed within the tubular case. Further, the assembly comprises a driver sub coaxially coupled to the lower end of the tubular case. The driver sub includes an upper end disposed within the case and a lower end extending axially from the lower end of the case. Still further, the assembly comprises a hammer bit coaxially disposed within the driver sub. The hammer bit including an upper end disposed within the driver sub and a lower end extending from the lower end of the driver sub. The upper end of the driver sub extends axially from the upper end of the hammer bit and is adapted to receive the piston.

Abstract: A method of manufacturing a percussion drilling assembly, the method including providing a tubular case having a central axis and a lower end with an inner surface and an outer surface, providing a driver sub having a central axis, an outer surface, and an upper end, providing a annular locking member including an annular body, an inner finger extending radially inward from the body, and a first outer finger extending radially outward from the body, positioning the annular locking member about the driver sub, and threading the upper end of the driver sub to the lower end of the case. The inner surface of the lower end includes internal threads and the outer surface of the lower end includes a groove. The outer surface of the upper end includes external threads and the outer surface axially below the outer includes a groove.

Abstract: A percussion drilling assembly for drilling through earthen formations and forming a borehole. In some embodiments, the drilling assembly includes a retainer sleeve having an upper end with an outer diameter and a tubular casing engaging the retainer sleeve. The tubular casing includes a first, second, and third tubular portion. The first tubular portion engages the upper end of the retainer sleeve at a first end having an outer diameter substantially equal to the outer diameter of the retainer sleeve. The second tubular portion is connected to the first tubular portion at a first end and has a second end with an outer diameter that differs from the outer diameter of the retainer sleeve. The third tubular portion is coupled to the second tubular portion. The first and third tubular portions each have a length configured to enable gripping of the tubular casing using tongs.

Abstract: A method of manufacturing a percussion drilling assembly, the method including providing a tubular case having a central axis and a lower end with an inner surface and an outer surface, providing a driver sub having a central axis, an outer surface, and an upper end, providing a annular locking member including an annular body, an inner finger extending radially inward from the body, and a first outer finger extending radially outward from the body, positioning the annular locking member about the driver sub, and threading the upper end of the driver sub to the lower end of the case. The inner surface of the lower end includes internal threads and the outer surface of the lower end includes a groove. The outer surface of the upper end includes external threads and the outer surface axially below the outer includes a groove.

Abstract: A percussion drilling assembly for boring into the earth. In an embodiment, the assembly comprises a tubular case having a central axis and a lower end. In addition, the assembly comprises a driver sub having an upper end threadingly engaged with the lower end of the case. Further, the assembly comprises a annular locking member disposed about the driver sub. The annular locking member engages the case and the driver sub and restricts the rotation of the driver sub relative to the case about the central axis.

Abstract: A percussion drilling assembly for boring into the earth. In an embodiment, the assembly comprises a tubular case having a central axis, an upper end, and a lower end. In addition, the assembly comprises a piston slidingly disposed within the tubular case. Further, the assembly comprises a driver sub coaxially coupled to the lower end of the tubular case. The driver sub includes an upper end disposed within the case and a lower end extending axially from the lower end of the case. Still further, the assembly comprises a hammer bit coaxially disposed within the driver sub. The hammer bit including an upper end disposed within the driver sub and a lower end extending from the lower end of the driver sub. The upper end of the driver sub extends axially from the upper end of the hammer bit and is adapted to receive the piston.

Abstract: A percussion drilling assembly for boring into the earth. In an embodiment, the assembly comprises a tubular case having a central axis and a lower end. In addition, the assembly comprises a driver sub having an upper end threadingly engaged with the lower end of the case. Further, the assembly comprises a annular locking member disposed about the driver sub. The annular locking member engages the case and the driver sub and restricts the rotation of the driver sub relative to the case about the central axis.

Abstract: A percussion drilling assembly for drilling through earthen formations and forming a borehole. In some embodiments, the drilling assembly includes a retainer sleeve having an upper end with an outer diameter and a tubular casing engaging the retainer sleeve. The tubular casing includes a first, second, and third tubular portion. The first tubular portion engages the upper end of the retainer sleeve at a first end having an outer diameter substantially equal to the outer diameter of the retainer sleeve. The second tubular portion is connected to the first tubular portion at a first end and has a second end with an outer diameter that differs from the outer diameter of the retainer sleeve. The third tubular portion is coupled to the second tubular portion. The first and third tubular portions each have a length configured to enable gripping of the tubular casing using tongs.

Abstract: A hammer bit for drilling a borehole in earthen formations. In an embodiment, the bit comprises a bit body having a bit axis and a bit face. The bit face includes an inner region extending from the bit axis to about 50% of the bit radius and an outer region extending from the inner region to the outermost radius. In addition, the bit comprises a plurality of gage cutter elements mounted to the bit face in a circumferential gage row in the outer region. Further, the bit comprises a plurality of adjacent to gage cutter elements mounted to the bit face in a circumferential adjacent to gage row in the outer region. The cutting profile of at least one cutter element in each row in the outer region radially overlaps with the cutting profile of at least one other cutter element in a different row in rotated profile view.

Abstract: A drive collar is disclosed for use in a percussion drilling apparatus of the type for boring into the earth. Embodiments of the drive collar include a generally tubular, one-piece body further having an inner surface, an outer surface, a first end and a second end. Embodiments further include a threaded section on the outer surface, a retention mechanism on the inner surface, a plurality of splines on the inner surface; and a shoulder on the outer surface.