NDE in the mass production automotive industry uses single frequency eddy current test systems for component parts integrity testing. Typical measures accomplished are: surface hardness (Rc), depth of hardened layer (case depth), core hardness, and soft spots on the surface caused by incorrect quench. Additionally, gross crack and seam defects are detected in production processes by this type equipment, on the order of .005" deep and .2" long. Some special results occur, such as: fillet combined hardness and case depth tests result in a direct correlation to fatigue life for the crankshafts of diesel engines.