Abstract: A device for sharpening saw chains while the saw chain is mounted on a chain saw cutting bar. The saw chain sharpening device is designed for use by a chain saw operator at the job site. The device comprises a frame configured to be straddle mounted over the saw chain and removeably clamped to the cutting bar. The frame has mounted thereon at least one pair of diammetrically opposed bushings having an inside diameter to accept a saw file and to permit the file to be slideably moved and axially aligned with the axis of alignment positioned relative to the saw chain so that the saw tooth being filed will be filed at the proper angle. The file guide bushings also provide precise control of the saw file position relative to the saw tooth being sharpened.