Abstract: A coupling assembly for a vertical in-line pump and motor combination in which all axial and radial loads are carried by bearings in the motor. The shafts have spaced apart ends and the pump shaft end includes an internal threaded bore. The coupling assembly includes an annular motor shaft hub, an annular pump shaft hub, an adjustment mechanism comprising a threaded shaft to be threaded into the threaded bore in the end of the pump shaft and an adjustment nut secured to an upper end of the threaded shaft, and an annular disc spacer. The components are secured together by axial bolts. Clearance between the pump impeller and its casing is set by rotation of the adjustment nut prior to insertion of the bolts. Completion of the assembly of the coupling establishes the operating clearance for the impeller and the coaxial positioning of the pump shaft to the motor shaft.