Abstract: A reversible ratchet for driving a socket wrench includes a ring gear which constantly meshes with an inner gear adapted to turn about an axis that is eccentric with respect to the axis of the ring gear. When the ratchet is turned in a driving direction, a crescent-shaped member wedges between the two gears and causes the ring gear to transmit torque to the inner gear in order to drive the socket. When the ratchet is turned in the opposite direction, the crescent moves out of wedging engagement with the gears and permits the inner gear to turn about its own axis as the teeth of the ring gear roll into and out of the teeth of the inner gear. Because the gears contantly mesh with one another, the drive picks up immediately when the ratchet is turned in the driving direction and thus the ratchet may be used effectively in very close quarters.