Abstract: A mechanism for detachably mounting any selected one of several attachments to a hollow spindlehead ram within which a spindle is rotatably supported by a hollow shaft, the latter being capable of both rotary and axial displacement relative to the ram. Both the hollow shaft and the selected attachment are coupled with the ram via Curvic coupling teeth. Further, in order to retain the attachment in positive engagement with the ram via the Curvic coupling teeth, a series of external locking teeth are formed on the hollow shaft at constant circumferential spacings for engagement with a series of internal locking teeth formed on the attachment. The hollow shaft forces the attachment against the ram via the interengaged locking teeth under hydraulic pressure.