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How to Measure Torque & the Tightening of Bolts

by Amber Viescas

Torque is a measure of rotational or "twisting" force. Measuring torque while installing a bolt prevents the overtightening of bolts. Torque wrenches are the most commonly used measures for this torque. They measure the torque applied to the fastener as the wrench tightens the bolt. In the early 20th century, engineers used analog meters. Nowadays, many torque wrenches either are digital wrenches or are calibrated to sense when torque has exceeded a certain level and stop tightening.

Step 1

Choose a torque wrench for your bolt. A "click wrench" tightens bolts to a particular specification, but cannot measure the torque of existing bolts directly. A mechatronic or digital torque wrench provides a readout of torque, but may prove difficult to read in tight spaces such as a car's interior.

Step 2

Loosen the bolt with an ordinary wrench, if you are using a click-type torque wrench. Set the dial on the torque wrench's handle to the desired level of torque.

Step 3

Fix the torque wrench over the bolt whose torque you want to measure and begin to tighten. Keep an eye on the digital readout, if you are using a digital wrench.

Step 4

Tighten the bolt until the desired level of torque is reached, or just until you see the bolt turn if you are using a digital wrench. A click torque wrench will slip once the torque becomes greater than the preset amount, with a cracking sound.

Read the torque measurement off the digital wrench, if applicable.

Items you will need

  • Torque wrench

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