Impact wrenches basically have to different types of torque control.
Conventional impact wrenches provide a torque output setting, but it is really up to the operator to determine when a nut is tight enough. These are some of the more common air tools found in the workplace.
Torque control impact air tools will shutoff at the predetermined torque setting. They are built for jobs that require accurate tightening. They incorporate built-in or detachable torsion bars. Based on their diameter and degree of adjustment, the torsion bar senses a predetermined torque level, and mechanically signals an internal shut-off device to prevent over-torquing