Torque screwdriver

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.

This is achieved with steel balls rolling between indented plates, compressed by a spring at one end, and the other side driving a screw or fastener.

In some cases a tool may need to be certified in a calibration lab to verify its torque output; a certificate may be issued by an organisation such as NIST in the United States.

They provide precision torque control and reduce energy consumption by eliminating idling.

The torque may be provided manually (by the operator's wrist), by an electric motor, or by a pneumatic drive.

Corded electric torque screwdrivers are commonly made in three different designs: pistol grip, angle and inline.

These tools must be near their compressed air source, not a problem in manufacturing but less suitable for general maintenance.