Abstract: A chuck for connecting a pressure device to a valve stem of a pressurized vessel includes a body portion having a first passageway that is configured to receive an outer tube portion of a valve stem of a pressurized vessel therein. The body portion has a guide portion at an inner end of the first passageway. A pin element is movably disposed within a second passageway of the body portion and is movable along the coaxial passageways. The pin element extends longitudinally from the guide portion and toward an engaging end of the body portion. The guide portion includes an alignment element at least partially around the second passageway and extending longitudinally toward the engaging end of the body portion and at least partially around the pin element for engaging and supporting an interior portion of the end of the outer tube portion of the valve stem.