Abstract: An improved fastener installation tool is provided of the type having a fixture pin for seated reception into a mating recess at the shank end of a threaded fastener, while a power-driven tool socket installs a threaded nut onto the fastener shank. The installation tool includes an improved spring-loaded clutch unit for normally supporting the fixture pin against rotation, but permitting fixture pin rotation in response to a torque load exceeding a predetermined limit thereby preventing fixture pin breakage. The clutch unit is adapted for quick and easy disengagement from the fixture pin, and pivotal displacement to an out-of-the-way position to permit quick and easy fixture pin removal and replacement.