MYTH: “1x RPM is always caused by unbalance.” TRUTH: Unbalance always causes vibration at 1x RPM.  However, 1 x RPM is not always caused by unbalance.  Many other problems can exhibit vibration at this frequency.  Examples are:  Misalignment, Bent shaft, bowed shaft, cracked shaft, eccentricity, open rotor bars in the motor, rubs, looseness, belt issues  [...]