Whichever comes first, to maintain optimal performance. The calibration procedure involves using specialized equipment, such as torque testers, to measure the wrench's accuracy. These testers apply controlled torque to the wrench, comparing its readings to known standards. This process identifies any discrepancies, allowing for necessary adjustments to bring the wrench within accept... https://zenithinstruments.com.au/pages/torque-wrench-calibration-services