A concentric alignment device is provided that elevates the working face of a drill bit off of the inner wall of a casing or tubing to prevent premature wear of the working face of the drill bit. In horizontal drilling applications, the working face of a drill bit has a tendency to contact or rest on the inner wall of a casing or tubing, which negatively affects the working face of a drill bit. In some embodiments, one or more optional inserts are provided on the shank of a drill bit or on a centralizing sub such that the inserts contact the inner wall of a casing or tubing instead of the working face of the drill bit. In other embodiments, blade packages on a drill bit or sub contact the inner wall of a casing or tubing and also pump drilling fluid in a downhole direction.

Various drill bits, drilling systems and related methods are provided. In one embodiment, a drill bit comprises a bit body having a face and a shank, at least one insert having a convex engagement surface coupled with the face and at least one wear insert coupled with the shank. In one particular embodiment, the at least one wear insert may be positioned immediately adjacent a coupling end of the shank. The at least one wear insert may include a superabrasive table which may be bonded with a substrate. The at least one wear insert includes a wear surface defined in the superabrasive table. In one embodiment, the superabrasive table may comprise polycrystalline diamond. Similarly, the inset having a convex engagement surface may include a superabrasive material, such as polycrystalline diamond, bonded with a substrate. Such a drill bit may be used, for example, in a top hammer percussion drilling operation.

A polycrystalline diamond drill bit for percussion drilling, in small holes in high silica ground. The bits are made having a bit body, and a series of insets locating in the bit body, and the bits are made using a double chisel design, or a modified double chisel design. The inserts are set into the bit body at very specific angles. The inserts have specific lengths to provide cut clearance for the bit body. The cutting angle the and radius on the tip of each insert in addition to the diameter of the inserts, provide a machine thrust pressure and machine torque pressure at low ranges when the PCD bits are used in percussion drilling.

A fixed cutter drill bit for drilling an earthen formation includes a bit body having a central axis and a bit face. The bit body is configured to rotate about the central axis in a cutting direction of rotation. The bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit. The drill bit also includes a cutting structure disposed on the bit face. The cutting structure includes a primary blade extending radially from proximal the bit axis through the cone region and the shoulder region to the gage region. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side. In addition, the drill bit includes a plurality of high-aspect ratio cutter element assemblies mounted to the cutter-supporting surface of the primary blade in the cone region. The cutter element assemblies are arranged in a radially extending row proximal the leading side of the primary blade, wherein each cutter element assembly includes a cutter element carrier and a first cutter element fixably attached to the cutter element carrier. Still further, the drill bit includes a plurality of low-aspect ratio second cutter elements directly mounted to the cutter-supporting surface of the primary blade in the shoulder region or the gage region. The second cutter elements are arranged in a radially extending row proximal the leading side of the primary blade. Each high-aspect ratio cutter element assembly has an exposure H1 measured perpendicularly from the cutter-supporting surface of the primary blade to a cutting tip of the first cutter element of the cutter element assembly distal the primary blade. Each low-aspect ratio second cutter element has an exposure H2 measured perpendicularly from the cutter-supporting surface of the primary blade to a cutting tip of the second cutter element distal the primary blade. The exposure H1 of one or more high-aspect ratio cutter element assemblies in the cone region is greater than the exposure H2 of one or more low-aspect ratio second cutter elements in the shoulder region or the gage region.