The present invention relates generally to butterfly valves and more particularly to butterfly valves having an improved cartridge type construction with improved bearings for the valve shaft. In the butterfly valve art valves have been constructed wherein the valve seat, the actuator shaft, and the valve disc are removable from the valve as a single unit, thereby facilitating repair of the valve in the field. For example, U.S. Pat. Nos. 2,740,423 and 2,994,342 to Stillwagon and U.S. Pat. No. 3,241,806 to Snell, Jr. all illustrate such a concept. However, to date, no such valve has been developed which is capable of dead-end service, i.e. retaining pressure within a line when the valve is in the closed position and the conduit on one side of the valve has been removed. Another problem that has existed with such valves is that the bearing required for the disc shafts have been difficult to align. Therefore, rather expensive machining operations have been necessary to provide good shaft alignment.