ABSTRACT: Fatigue failures results from repeated localised plastic deformations in a machine member caused by variable loads and typially occurs at stress levels significantly lower than the yield strength of the material, usualy after thousands-even millions-of cycles of minute yielding that often exists only on a microscopic level. Fatigue fractures start wiyh a tiny (usualy microscopic) crack at a critical area of high local stress, wich enlarges until the section is sufficiently weakened so a final fracture occurs on one final load. Highly localised plastic yielding can be the start of a fatigue failure, notably in holes, sharp corners, threads, keyways, surface scratches and corrosions. Although the phenomena of fatigue has been known for over 150 years, such failures are very common; over 80% of mechanical breakdowns are from fatigue. They do not give any visible warning, it is sudden, total and catastrophic. As such, knowledge of fatigue calculations is very important for every machine designer. The author has found different methods and equations for fatigue calculations in Swedish and American higher education textbooks, given different results. In the article, the author focuses on different shaft designs for infinite fatigue life that of different cyclic loading, using Swedish and American methods to compare the results.