An innovative air driven spindle for micro-milling applications is presented, in which a so-called viscous turbine is used to both drive and support the spindle. The viscous turbine drives the spindle by exerting viscous traction forces directly on the smoooth surface of the spindle. It is even possible to use a standard millling tool directly as spindle, thereby rending a tool holder, with its inherent inaccuracies, redundant. Furthermore the viscous turbine not only drives the took, but also functions as an aerostatic radial bearing. In this paper the viscous turbone concept is presented, and an optimasation for the pertinant design dimensions is carried out using a simplified analyutical model. A prototype spindle design is presented, and the results of the first experiments are analysed and improvement for the second prototype are proposed.@en