Machine parts are very frequently submitted to continuous operating loads, therefore have to be very carefully designed to avoid undesirable stress concentration. A number of research studies have shown that besides the design itself an important role is played also by the stress state created in the material by carelessly planned manufacturing technologies. Internal stresses which are, since the completion of manufacturing, termed residual internal stresses very much reflect the manufacturing procedures and machining conditions. The measurements of residual stresses were carried out by the relaxation method based on the electro chemical removal of the stressed surface layer. The anode dissolution results in a newly created eyuilibrium state which was followed by measuring the deformation during the removal. From the time variation of the deformation of the specimen material and the known depth of the removal at the given moment, it is possible to calculate the size of residual internal stresses as a function of depth of the stressed surface layer. Residual internal stresses are analyzed for different surface hardening conditions and also after grinding at different machining conditions.