Abstract: Chuck for use with manual or powered driver having rotatable shaft, the chuck including a body member and jaws slidably positioned in angled passageways formed in the body. The chuck further includes a nut rotatably mounted relative to the body member and in engagement with threads on the jaws. A generally cylindrical front sleeve member is disposed in driving engagement with the nut and overlying the nose section of the body so that when the front sleeve member is rotated with respect to the body, the jaws will be moved thereby to grip the shaft of a tool. A spring member is biased to engage the sleeve member and is disposed selectively rotatably with respect to the nut. When the nut is tightened, the spring member becomes locked to the body member and restrains the nut from loosening during vibration of the chuck in use for its intended purpose.