Abstract: An apparatus for rapid interchange of drive head units on a power tool motor unit is provided by forming a flared lip on the first of the two housings to be connected; capturing a coupling nut behind the flare with a split clamp ring; forming a bore on the second housing into which the flared lip and clamp ring of the first housing will fit; forming a positioning stop, within the bore, against which the flared lip of the first housing will be clamped; and providing a coupling device on the second housing to which the coupling nut of the first housing will be coupled to join the two housings.