This paper presents a method for the quality control of a bolted assembly by monitoring its tightening. Both torque and angle are already used in the production lines as target values, but the proposed method also uses them as a means of verification. In fact, the variations of the stiffness of the bolt through the torque-angle relationship is a good indicator of the bolt’s interface quality and thus of the performance of the overall assembly. The impact of gaps and friction on this relationship are investigated using a full 3D finite element model.