Abstract: A shaft coupling system (10) is used to connect one shaft (23) to another shaft (44). The system (10) is suited for use in the environment of a pump (11) having a motor assembly (12) and a disposable pump assembly (13). The shaft (23) is driven by a motor (15) and carries a drive coupling device (24). The shaft (44) of the pump assembly (13) carries an impeller (47) at one end and a driven coupling device (49) at the other end. The drive coupling device (24) includes lugs (55) having helical guide surfaces (57, 58) and a helical drive surface (56). The driven coupling device (49) includes fingers (64) having helical guide surfaces (66, 67) and a helical driven surface (65). When the coupling devices (24, 49) are axially engaged, the guide surfaces (57, 58 and 66, 67) may engage each other and rotate the coupling devices (24, 49) relative to each other to position the fingers (64) between the lugs (55).