AbstractThis paper presents the failure analysis of the rod of an oleo-hydraulic cylinder of a machine for fatigue testing large diameter heavy duty cables for marine applications. A distinct feature of this machine is its size: the 3990 mm long rod has an outside diameter of 340 mm. The rod is manufactured machining a solid cylinder of 42CrMo4 steel, along most of its length, into an hollow cylindrical rod with inside diameter 165 mm. Typical maximum loads applied are of the order of 10000 kN. In one of the extremities where load is applied, the rod is solid (not hollow), and the complete fracture occurred in the transition of the solid to the hollow parts, during a test performed under maximum load of 8200 kN under R (load ratio) of approximately 0.The fracture is flat and perpendicular to the rod axis, ie to the load direction, revealing a smooth surface appearance. Fracture surface roughness increases from the inner to the outer radius. Close to the outer radius evidence of ring-like beach marks was found. The fracture was due to fatigue cracking initiated at the fillet radius of the transition solid/hollow rod, and propagated until complete, sudden fracture.The paper discusses this case in the light of (i) a conventional Soderberg approach, and (ii) a DIN 743 analysis. Lessons learned in the case, particularly as concerns a comparison of the typical Soderberg approach and the DIN 743 procedure, are presented.