Torque Wrench
A specialized hand tool used to precisely apply a specific torque to a fastener, such as a lug nut or cylinder head bolt.
A torque wrench is a precision measuring tool designed to apply a specific amount of rotational force (torque) to a threaded fastener, such as a bolt, nut, or spark plug. In automotive mechanics, proper tightening is critical: under-tightened fasteners can back out and loosen due to vibration, while over-tightened fasteners can stretch, strip threads, or warp mating surfaces (like cylinder heads or brake rotors).
Torque wrenches come in several styles, including click-type (which emits an audible click when the set torque is reached), beam-type (which uses a flexing pointer over a scale), and digital-type (which displays real-time torque and alerts the user with lights and beeps). They are calibrated in units of foot-pounds (ft-lbs), inch-pounds (in-lbs), or Newton-meters (Nm).
To maintain its accuracy, a torque wrench must be handled with care and stored properly. Click-type torque wrenches should always be wound back down to their lowest setting before storage to relieve tension on the internal spring. It should never be used to loosen stuck bolts, as this can damage the internal calibration mechanism.