Studies of interference fitted connections show that the traditional design method based on thick-wall cylinder theory has some limitations. Application of the finite element method for the elasto-plastic stress analysis of interference fitted connections gives more complete and accurate results than the traditional method. In this study, stress and separation frequency analyses of interference fitted connections for all preferred diameter series and all preferred hole basis interference fits was carried out. The results showed that the traditional design method was not usable for all thick-walled interference fitting and diameter/interference ratio was decisive for accuracy of results obtained from traditional design methods. For smaller ratio than 750, the results obtained from traditional design method were not viable. The results also showed that designers should pay attention to separation frequencies and decreasing pre-stresses using 100-500 mm of shaft diameters during interference fitting. (C) 2011 Elsevier Ltd. All rights reserved.