This invention relates to a fastener driving device including a variable ratio gear mechanism that enables the ratio of the rotation of the handle to the rotation of a driving bit extending from the handle to be varied to allow the bit to rotate at different speeds from the handle. The device includes a gear mechanism disposed within a housing for the device that includes a locking member. The locking member can be engaged with the gear mechanism to lock the gear mechanism in a configuration for a 1:1 gear ratio. The locking member can be moved with regard to the gear mechanism to provide an increased gear ratio for the gear mechanism when desired.