Abstract: A percussion drilling assembly includes a housing with a hammer bit disposed in the lower end portion thereof and configured to move longitudinally within the housing. The hammer bit includes an annular bit shank having a bit strike face and a cutting structure at a lower end portion thereof. An annular piston having a piston strike face arranged and designed to strike the bit strike face is also disposed in the housing. At least one of the bit strike face and the piston strike face has a toroidal curvature profile. A method includes one or more of lowering the percussion drilling assembly into a borehole, engaging the cutting structure with a formation, and impacting the bit strike face of the annular bit shank with the piston strike face of the annular piston.

Abstract: A roller cone drill bit having a bit body. The bit body has a journal bearing coupled to an end portion thereof. A roller cone is coupled to the journal bearing. A first cutting element is coupled to the roller cone. A ratio of a radius of curvature of a crest portion of the first cutting element to a diameter of the first cutting element is between about 0.3:1 and about 0.8:1. A second cutting element is coupled to the roller cone. A ratio of a radius of curvature of a crest portion of the second cutting element to a diameter of the second cutting element is between about 0.05:1 and about 0.3:1. A height of the second cutting element is greater than the height of the first cutting element h between about 0.1 mm and about 6 mm.

Abstract: A cutting insert for a percussion hammer bit. The cutting insert includes a base portion for coupling to a bit face of the percussion hammer bit. An extension portion is coupled to the base portion and axially offset therefrom along a longitudinal axis extending through the base portion and the extension portion. The extension portion includes at least three lobes that are circumferentially offset from one another around the longitudinal axis. The lobes extend axially away from the base portion, and the lobes extend radially outward from the longitudinal axis.

Abstract: A percussion drill bit for drilling a borehole. The drill bit includes a bit body having a bit face disposed on an axial end portion thereof. First and second cutting elements are disposed on the bit face. A cutting plane is defined in tangential contact with crest portion of the first and second cutting elements. A third cutting element on the bit face is at least partially positioned between the first and second cutting elements. The third cutting element is at least partially conical, and a crest portion of the third cutting element is offset from the cutting plane.

Abstract: A percussion drilling assembly includes a housing with a hammer bit disposed in the lower end portion thereof and configured to move longitudinally within the housing. The hammer bit includes an annular bit shank having a bit strike face and a cutting structure at a lower end portion thereof. An annular piston having a piston strike face arranged and designed to strike the bit strike face is also disposed in the housing. At least one of the bit strike face and the piston strike face has a toroidal curvature profile. A method includes one or more of lowering the percussion drilling assembly into a borehole, engaging the cutting structure with a formation, and impacting the bit strike face of the annular bit shank with the piston strike face of the annular piston.

Abstract: A hammer bit retainer system includes a hammer bit locking mechanism arranged and designed to prevent decoupling of a driver sub from a hammer casing. The hammer bit locking mechanism includes an expandable split ring which is disposed in the coupling between the driver sub and hammer casing. The hammer bit locking mechanism prevents axial movement of the driver sub relative to the hammer casing in at least one direction.

Abstract: A percussion drilling assembly for drilling a borehole, the assembly including a tubular casing having a central axis defined therethrough and a lower end, a driver sub having an upper end threadingly engaged with the lower end of the tubular casing, and an annular locking member disposed between the tubular easing and the driver sub. The annular locking member is configured to engage the tubular casing and the driver sub, and is configured to prevent separation of the driver sub from the tubular casing. The annular locking member includes a deformable elongate member.