Torque wrench

A torque wrench is a wrench with an internal mechanism that measures the torque (rotational force) being applied to a fastener and signals when a preset value is reached. It ensures bolts are tightened to the manufacturer’s specification — neither too loose nor too tight.

How it works

You set the desired torque on the wrench’s scale (by turning a dial, ring, or digital interface). As you tighten the fastener, the wrench measures the applied torque. When the target is reached, the wrench signals the user — typically with an audible click, a tactile pulse, or a digital readout.

Types

• Click-type torque wrench: The most common type. An internal spring-loaded mechanism releases at the preset torque, producing a distinct “click” that you feel and hear. Stop tightening immediately when you feel the click.
• Beam-type torque wrench: Uses a deflecting beam and a scale. The beam bends as torque increases, and you read the value on a pointer. Simple, reliable, and requires no calibration — but less precise than click-type.
• Digital torque wrench: Uses a strain gauge and electronic sensor to display the torque value on an LCD. Some models vibrate, beep, or light up when the target is reached. The most precise type.
• Dial-type torque wrench: Has a dial gauge that shows the torque in real time as you tighten. Good for monitoring torque during tightening, not just at the endpoint.

Why torque wrenches matter

• Safety: Over-tightened bolts can snap; under-tightened bolts can vibrate loose. Both are dangerous.
• Consistency: A torque wrench ensures every bolt in a set is tightened to the same specification.
• Compliance: Many manufacturer service procedures specify exact torque values. Using a torque wrench is the only way to meet these specifications.

Care and calibration

Torque wrenches should be stored at their lowest setting (to relax the internal spring) and calibrated periodically — typically once a year or after a specified number of uses. Dropping a torque wrench can damage its accuracy.