A vacuum pump (1, 30) has an inlet (5) and an outlet (6). Plug-in screw fittings (9) are connected with the inlet and the outlet. The plug-in screw fittings include a bore with an internal bevel (22) that receives a flexible connecting line (23), a chuck collet (19), and an O-ring (21) frictionally in a vacuum-tight relationship. In this manner, a more simple and versatile connection is provided between the vacuum pump and the connecting lines.