Considerations on the improvement of the stiffness of bolted joints in machine tools.

The present paper deals with an improvement of the stiffness of bolted joints in machine tools. In the design of bolted joints, the stiffness, the bolt axial force and the distribution of the contact stress are important characteristics, and they have been investigated by many researchers. But the effects of the tightening position of the thread in a base, the height of clamped parts and the configuration of contact surfaces are not taken into consideration sufficiently. Thus, in the present paper, the effects of the tightening position of the thread in the base on the stiffness and the distribution of the contact stress are examined experimentally in the case where a beam is fastened partially to the base with tap bolts. As a result, it is shown that these effects contribute to the improvement of the stiffness of bolted joints.