Abstract: A mill assembly having a mill face for milling material in a downhole milling operation is received in a casing or well bore having an internal wall having a first diameter. The mill face has a smaller diameter than the first diameter. The mill face is connected to a shaft assembly including a shaft and a stabilizing assembly for stabilizing the shaft in the casing or the well bore. The stabilizing assembly is connected at one end to the mill face and has a smaller diameter than the first diameter. The stabilizing assembly includes a stem having one or more tapered surfaces, the tapered surfaces tapering from a first diameter to a second diameter larger than the first diameter. The stabilizing assembly further includes a plurality of roller bearings circumferentially arranged in a plane around the stem, each roller bearing being in contact with one of the tapered surfaces at a first point.