It is important to check the accuracy of your torque wrench because inaccuracy can cause too much or too little pressure to be put on a component. This will affect the performance ability of the component. Calibration of the torque wrench will ensure the correct amount of pressure is applied to the component. What could happen if a torque wrench that has not been calibrated is used? Components could break or fall apart.
How often should a torque wrench be calibrated?
Referencing ISO 6789:2003 will help to answer this question. The standard "specifies the requirements for, and describes the test methods and marking of, hand torque tools used for controlled tightening of bolted connections." Recalibration standards are also detailed in ISO 6789:2003; they state that torque wrenches should be recalibrated after 5000 cycles or 12 months. However, factors such as use frequency, general care, and setting of the wrench will affect the calibration. So, the wrench may need calibrated more often than the standard ISO 6789:2003 requires. Torque wrenches should be calibrated by laboratory accredited under ISO 17025:2005. This standard "specifies the general requirements for the competence to carry out tests and/or calibrations, including sampling. It covers testing and calibration performed using standard methods, non-standard methods, and laboratory-developed methods."
Proper care of the torque wrench will allow for it to remain calibrated for the maximum amount of time. Here are some tips on caring for your torque wrench:
1. Store the torque wrench in its case, and ensure it is in a dry area to prevent rust.
2. Do not store the torque wrench with its setting on zero. It should not be stored with the setting below the minimum scale marking, which is about 20 percent of the maximum. At the same time, the torque wrench should not be set on a high setting.
3. Do not operate the torque wrench near or at its maximum setting. If you want to check a torque level at 80-100 ft-lbs, then ideally you should use a torque wrench with a maximum setting higher than 100 ft-lbs.
4. If the wrench has not been used for a period of time, turn the knurled handle several times. This will lubricate the internal workings.
5. Clean the torque wrench using a cloth. Immersing the torque wrench in a cleaning solution can cause damage to the lubrication of the internal workings.
6. Have the torque wrench calibrated by a certified technician yearly, or more often if necessary.
The importance of ensuring the torque wrench you are using is properly calibrated cannot be stressed enough. The torque wrench should be calibrated at least once a year, or possibly more by a certified technician. AER provides torque wrench calibrating services at their laboratory under the proper standards.