A polar coordinates sensor probe, having a plurality of circularly arranged pick-up poles driven by a rotating magnetic field originating in a hollow toroid core, for detecting the reflected rotating eddy current pattern in material (both ferrous and non-ferrous) surrounding fastener holes, wherein the flaw is detected by means of mutual phase-amplitude comparison and adjacent pick-up pole signal phase deviation. The second embodiment having an isolated multi-pole pick-up core, picking up a rotating figure 8 eddy current pattern. Also embodiments utilizing Hall effect and magnetoresistive devices with the rotating magnetic field for flaw detection.