A torque screwdriver is a screwdriver with components that ensure tightening to a specified torque, ensuring tightening which is sufficient, but not excessive. An insufficiently tightened screw connection may loosen in operation, and excessive tightening can damage parts; for example, if the nuts holding the wheel of a car in place are too loose, or damaged by overtightening, a wheel may come off at speed. Torque screwdrivers are used in mechanical production, manufacturing, and maintenance; their use is part of quality assurance.
Most torque screwdrivers allow the torque to be set to any value within a range. All have a torque-limiting clutch that disengages once the preset torque has been reached.
Torque screwdrivers can exert torques from 0.04 N⋅m to at least 27 N⋅m. Although no single tool covers the entire range, low-, mid-, and high-torque ranges are available.
Torque screwdrivers and torque wrenches have similar purposes and mechanisms.