Abstract: An eddy current probe shaft with probe and drive mechanism attached for measuring integrity of a bolt hole, particularly useful for aircraft bolt holes, includes a continuous helical coil manufactured integrally into a one-piece steel shaft providing flexure in the shaft enabling axial self-alignment even when the shaft is inserted obliquely into a bolt hole. The intact, integrated helical coil of flexible steel provides a constant length probe, effectively noncompressible and nonelongatable, flexible under external bias and with a spring constant sufficient to reliably return the shaft to a straight-axis rest position upon release of the external bias. An eddy current probe with a test coil in a probe head is attached at the shaft distal end for measuring cracks and similar structural anomalies in the bolt hole. A drive mechanism is attached at the shaft proximal end for rotating the shaft and probe in the bolt hole for a circumferential scan of the bolt hole interior surface.