A hinge assembly and methods for mounting a hatch relative to a port defined in a cover of a vacuum chamber to close and open the port. A torsion rod mounted between the port and the hatch is in torsion when the hatch is in a closed position relative to the port, assisting port-opening motion. A sleeve surrounds the rod and is movable with the hatch. Friction hinge structures between the cover and the sleeve, and between the hatch and a second sleeve are in a friction-engaging relationship with the corresponding sleeve. Each friction hinge structure provides high resistance to relative motion between a friction spring and the corresponding sleeve. During the port-opening motion of the hatch the friction springs provide low resistance to such relative motion. The hinge structures provide tolerance resistance and vacuum compliance by allowing relative movement between a hinge mounting plate and the hatch. During vacuum pumping, the hinges allow the hatch to move from an O-ring pre-load position, to an intermediate position, and then to a final position so that the pre-loaded O-ring compresses to an operational O-ring compression. Since the hinges permit the O-ring pre-load position to exist prior to vacuum operation and under all variations of certain manufacturing tolerances, the full range of relative motion between the plate and the hatch is permitted, such that the sealing surfaces seal in a tolerance resistance and vacuum compliant manner.