Bolts normally have a 90° angle towards the mounting face of machine they fixate. The foundation however is in 99% of the cases not in parallel with the plane of the machine. The result is that the bolt is bending when tightening as the bolt head is touching at one point only. Consequently, the tightening torque is not converted in the calculated effect. The bolt will come loose in time.
 
A spherial washer between the bolt head and the foundation will absorb the difference in angle. In case where a short clamping length of the bolt is reducing the fixation eff ect of the bolt, spherical spacers are advised.
ExaktAlign's portfolio is comprising of both Spherical Spacers as Spherical Washers. The washers come is a standard execution (SW) and as Large washer with a bigger diameter (SWL). Below, the avalaible sizes are prenented.