Abstract: Apparatus for detecting defects such as fissures in the ferrous metal of elongated workpieces such as pipe may take the form of wall thickness and material continuity inspection apparatus that is located at an inspection site, with the inspection site being provided to receive an elongated metal workpiece such as a section of drill stem. A movable magnet support structure is located at the inspection site and carries a magnet and coil assembly in movable shoe means that is capable of engaging the outer periphery of the workpiece and establishing a predetermined spaced relationship between the workpiece, the magnet and the coil. The magnet support shoe, together with the magnet and coil, are movable in helical manner about the workpiece, causing the shoe to traverse the entire outer periphery of the workpiece during a single inspection pass.