Torque Wrench Calibration
In my last blog I wrote the importance of using a Torque Wrench to properly tighten the wheel nuts. It is also important to have the torque wrench calibrated to ensure their accuracy. How often it should be calibrated depends on its use. According to the American Society of Mechanical Engineers standard, a torque wrench used in automotive repairs should be accurate within +/-4% clockwise or +/-6% counterclockwise, from 20% of its scale to full scale.
For the commonly used clicker or micrometer torque wrench, the actual click is considered a cycle of the wrench. Most manufacturers recommend calibration after approximately 5,000 cycles, or once a year.
Torque wrench calibration can be tested in the service center. Torque wrench testers are available from manufacturers such as Snap-on as well as from Kent-Mooore SPX. Be sure the tester is four times as accurate as the wrench being tested. This means a 1% tester is needed for a typical 4% wrench. The tester will indicate the accuracy of the wrench. If it is out of range, calibration is required.