Abstract: An adapter for quickly and easily converting a portable, 71/4 inch wormdrive circular saw into a beam cutting chain saw, whereby to increase the cutting capacity of the saw from about 21/4 inches to about 12 inches. the adapter carries a standard cutting chain and includes a hinged attached assembly to be removably connected to the existing slide bars of the saw. The attachment assembly comprises a pivotal hinge and a hinge attachment plate. The hinge and/or the adjustment plate may be pivoted relative to one another to vary the effective length of the hinged attachment assembly and thereby facilitate the connection of the adapter to the slide bars of the saw. By adjusting the length of the hinged attachment assembly, the adapter can be selectively sized for use with virtually all commercially available power saws, regardless of the radial distance between the existing motor shaft and the slide bars of the saw.