Abstract: A tool is provided which is useful for loosening the locking collars of frangible fasteners which are commonly used in the aerospace industry. The tool includes a socket head having a through socket at one end thereof, an elongated handle having a jaw end forming an arcuate surface, and an assembly pin which extends through aligned handle and socket head apertures to pivotally attach the handle to the socket head. Two sets of gripping teeth are provided within the socket in an adjoining arrangement to one another along a longitudinal axis of the socket. The jaw end of the handle projects into the socket to grasp items therein, such as the narrow wall of a locking collar of a frangible fastener. Preferably, the arcuate surface of the handle forms an involute curve.