A fluid dynamic bearing including a shaft rotating within a sleeve and a thrust plate or the like supported at an end of the shaft rotating in a recess defined with the sleeve. The thrust plate faces a counterplate supported from the sleeve over the recess, and the sleeve and shaft are supported for rotation by fluid in the gap or gaps between the shaft and sleeve, thrust plate and sleeve, and thrust plate and counterplate. To prevent fluid from leaking out of the fluid dynamic bearing into the surrounding atmosphere by seeping between the counterplate and sleeve face it rests on, a seal recess is defined in the sleeve, a crush ring seal is placed in the recess. The counterplate is then pressed into the recess, crushing the crush seal ring and blocking any passage of the fluid from the gap region surrounding the thrust plate through the gap between counterplate and sleeve. The crush seal may preferably be either in an o form, a block form or an x form, and may be solid or hollow, preferably of a material which expands at approximately the same rate as the surrounding sleeve and counterplate. Preferred materials from which the crush seal may be selected include aluminum, brass, copper, and steel.