[CS4] 3D rotation via AS resets pivot point?

Trying to make a gearshift. I’ve set the 3d rotation point of the head and shaft to the base of the shaft. But when I execute the following code:

function frEvt(e:MouseEvent):void{
    if (bDrag){
        mcHead.rotationX = nStartRot + (nStartY - e.stageY)
        mcShaft.rotationX = mcHead.rotationX
        mcSheath0.rotationX = mcHead.rotationX*.75  //These are the segments of the rubber cover at the base
        mcSheath1.rotationX = mcSheath0.rotationX*.75
        mcSheath2.rotationX = mcSheath1.rotationX*.75

They just spin in place around their center points, rather than move as one object. How do I adjust the origin for rotationX/Y/Z in AS3?