A helical anchor capable of use in high load-bearing capacity applications involving extreme drive torque conditions, the anchor having a main drive shaft machine fabricated with an integrally formed hardened alloy steel coupling section that is adapted to mate with a similarly hardened and integrally formed corresponding coupling section of an extension shaft. The coupling sections are formed of seamless high-carbon heat-treated alloy steel which is quenched and tempered to a yield and tensile strength approximating 135,000 psi, and inertia friction welded to the hot-finished seamless alloy steel tubing utilized in the formation of the remainder of the drive and extension shafts.