Abstract: An expandable drilling apparatus includes a main body comprising a central bore and at least one axial recess configured to receive an arm assembly operable between a retracted position and an extended position, a biasing member to urge the arm assembly into the retracted position, a drive position configured to thrust the arm assembly into the extended position when in communication with drilling fluids in the central bore, a selector piston translatable between an open position and a closed position, wherein the selector piston is thrust into the open position when a pressure of the drilling fluids exceeds an activation value, wherein the drilling fluids are in communication with the drive piston when the selector piston is in the open position, and a selector spring configured to thrust the selector piston into the closed position when the pressure of the drilling fluids falls below a reset value.

Abstract: Steel bit bodies are manufactured with polystyrene patterns in a lost foam casting process. The patterns are machined in complex shapes that cannot be extractable from reusable, two-piece pattern molds. The patterns are machined in a basic, programmed, five-axis machining process to form multiple copies of a complex pattern body. The process is modified to produce multiple copies of a modified design. Multiple bit patterns of variable forms are produced without an intermediate, reusable pattern mold that would require multiple mold pieces, thus eliminating the time and expense in variation of the bit design. The pattern is machined in a single chucking operation in a machine tool adapted for machining plastics in a three-dimensional global process. The plastic composition and density permit it to be machined into a pattern having relatively small, unsupported structural projections and smooth surface features.

Abstract: Steel bit bodies are manufactured with polystyrene patterns in a lost foam casting process. The patterns are machined in complex shapes that cannot be extracted from reusable, two-piece pattern molds. The patterns are machined in a basic, programmed, five-axis machining process to form multiple copies of a complex pattern body. The process is modified to produce multiple copies of a modified design. Multiple bit patterns of variable forms are produced without an intermediate, reusable pattern mold that requires multiple mold pieces, thus eliminating the time and expense in variation of the bit design. The pattern is machined in a single chucking operation in a machine tool adapted for machining plastics in a three-dimensional global process. The plastic composition and density permit it to be machined into a pattern having relatively small, unsupported structural projections and smooth surface features.