In this study, a computer program was developed using Q-Basic programming language to analyze the strength and deformation of a rotating circular stepped shaft. These shafts have a variety of power-transmitting mechanical elements (components), such as pairs of gears, and pulleys that are modeled in 3-D. In addition, force and moment analyses of these elements running on the shafts are examined. Notch sensitivity and stress concentration factors given graphically were formulated using the finite difference method. Furthermore, to select the best rolling-contact bearings, an expert system requiring the knowledge-based technique was employed. The knowledge of the expert system and data of the rolling bearing catalogue were input into the program. To perform the expert system, the LEONARDO software technique was used.