Non-Destructive Testing (NDT) are techniques applied to materials and equipment inspection without integrity degradation and can be performed in the post-manufacture, assembly, operation and maintenance stages. Those techniques are used by the industry to control a guarantee the quality of materials, products and processes. The aim of this research was to identify cracks and estimate their length on DIN 42CrMo4 steel specimens adopting different NDT techniques. The material to the test specimen was taken from a crankshaft of a Diesel engine, utilized as generating units in thermoelectric power plant, which has failed due to low cycle fatigue. The test specimen were designed according to ASTM E1820, ASTM E1290 and ISO 15653 standards, as well as suggestions made by NDT inspectors for a geometry that optimized the efficiency of the measurement. Subsequent to the fatigue induced crack on the specimens, they were inspected using, Digital Radiography (RD), Phased Array Ultrasound (UT-PA), Pulse-Echo (PE) and Time of Flight Diffraction (ToFD) methods, and Digital Tomography (TC). The specimens were then fractured with a bending load and liquid nitrogen, which allowed the measurement of the real crack length. UT-PA, PE and ToFD, and RD techniques showed a closer estimate crack size among then. It was observed that both UT-PA methods, PE and ToFD, presented an influence of the distance between the equipment head and the crack position, on the crack measurement. This was more pronounced in smaller cracks, leading to an erroneous measurement of the crack length. The RD technique presented a good a good result of lateral crack length, but a good digital image processing was necessary to obtain these results, explained by the sensitivity of the test to the geometry to the geometry of the specimen and to the material density. TC presented better imaging and similar lateral crack lengths when compared to RD, which could influence the detection of other types/dimensions of defects. In contrast, it is more influenced by the volume of material around the object, which made it impossible to detect defects in some samples.