The present disclosure describes a magnetic fluid sealing device having a shaft centered with respect to a magnetic structure and rolling element bearing, as well as a method for centering the shaft in the device. A compressible ring located in a groove on the shaft is used to partially fill the gap between the shaft and the rolling element bearing and to make contact with the rolling element bearing. The compressible ring aligns and centers the shaft with the rolling element bearing. A liquid locking material is added to the gap and hardened to couple the shaft and compressible ring to the rolling element bearing. An alternative self-alignment mechanism is also disclosed.