A coupling mechanism for a molten metal processing system includes an elongated shaft having an upper axial end and a lower axial end. A passage having a torque facilitating shape extends through at least a portion of the shaft. The upper end of the shaft tapers inwardly and forms a tapered seat. At least one channel is machined into an outer surface of the upper end of the shaft. The channel has a first portion extending longitudinally downward from a top surface of the shaft and a second portion extending from the first portion at an angle greater than 90° relative to the first portion. A coupling member, for coupling the shaft to a drive system, includes a body having an annular wall which defines a cavity. At least one locking member is disposed on an inner surface of the annular wall which is adapted to cooperate with the channel in the shaft. The locking member is aligned with the first portion of the channel and the shaft is slid into the cavity. When the locking member reaches a bottom surface of the first portion of the channel, the shaft is turned less than one third of a rotation so that the locking member travels partially across the second portion of the channel thereby pulling the shaft upward. The cavity of the coupling member tapers outwardly forming a mouth which engages the tapered seat of the shaft in a sealing relationship.