Drilling/tapping/unscrewing apparatus

A drilling/tapping/unscrewing apparatus comprising a transmission shaft of a power source, a drilling ratio gear mounted on the transmission shaft, a tapping ratio gear mounted on the transmission shaft and an unscrewing ratio gear mounted on the transmission shaft in a housing, the power of the power source via the transmission shaft and the gears being transmitted to a bit, the apparatus further comprising an adjustment unit for controlling the drilling, tapping and unscrewing operations of the apparatus, said apparatus being characterized in that the adjustment mechanism includes a bit shaft on which a drilling gear, a tapping gear and an unscrewing gear are fitted, the tapping gear and the unscrewing gear being respectively engaged with the tapping ratio gear and the unscrewing ratio gear, the drilling gear and the tapping gear being controlled by an adjustment button to synchronously move up and down on the bit shaft, whereby the drilling gear can be engaged with or disengaged from the drilling ratio gear.