Abstract: A contra-angle housing made in two parts hinged together at one end encloses a drive shaft with drive gears at one end, and a geared hub for a dental tool or the like supported in apertures in or through the housing parts transverse to the drive shaft. A latch mechanism can be manually operated to release the two housing parts so that they can be opened to change tools, clutches or the like with integral gear hubs. When the housing parts are closed the gears on the hub automatically mesh with the drive shaft gears. Reinforced gears which can be made of molded plastic make possible low-cost interchangeable tools with integral gears.