This paper deals with the evaluation of the stress concentration at the thread grooves of bolts where they are engaged with nuts. The thread grooves treated here are the metric coarse screw threads and those the authors have already proposed in order to reduce the stress concentration. The parameters considered are the combinations of the mechanical properties of four parts those are the bolt, nut, washer and fastened plates. The transmitted forces at the thread ridges are firstly analyzed considering these four parts. The bolt itself is then precisely analyzed using the above results as the external forces.
