Abstract: A novel air-driven screwdriver is integrally designed to perform three functions, hole drilling, thread tapping and bolt tightening with special characteristic in which a passive inner gear assembly is employed as a driver to replace the clutch as used by the prior art. When the torque reaches at a specified level, the cam in the inner gear assembly will jump up and down, working similarly as the clutch, coupling with the torque spring and torque adjusting mechanism to control the output of the actual torque applied. This design eliminates the attachment of the clutch, shortens the overall length of tool, reduces the total weight and becomes more practical and reliable tool machine.