How often should I calibrate my torque wrenches?
Calibration Intervals for S/R Torque Wrenches

S/R recommends using data-driven calibration intervals for torque tools.

Torque wrenches and torque screwdrivers are measurement instruments that also perform work. Most measurement instruments are used before and/or after work is performed. They are not required to perform the work itself. As an example cutting tools perform the work of cutting material, after which the caliper or micrometer measures the output. The cutting tool wears when it performs the work. The pure measurement tool wears as well, but at a vastly lower rate.

Torque wrenches and torque screwdrivers wear more like a tool than like a measurement instrument. The calibration interval needed to keep them in calibration is a function of use rate, just as it is with other tools that perform work. A tool that is used to torque twenty fasteners per day will have a different accuracy retention period than that of the same tool used to torque 1,000 fasteners per day.

The wear rate is also a function of accumulated use. The accumulated wear of a tool that has been used to tighten 300,000 or 400,000 fasteners will be significantly different than the tool used to tighten 1% as many, even when both have been in service for the same period of time.

The wear rate is also a function of the percentage of tool capacity at which the tool is routinely used. A tool used near 100% of rated capacity will wear at a rate different from one routinely used at 50% of capacity, even when both are used for the same number of cycles each day.

Our torque tools are used in a variety of roles in a very wide variety of industries. We cannot know the use rate, capacity percentage, or total cycles for the tools we provide. Further, these shift over time; the total number of cycles on the tool changes with each use, the operation the tool is used on, and the percentage of it’s capacity, may be changed at any time, and the daily throughput is also a variable.

For these reasons S/R recommends calibration at data-driven intervals throughout the life of the tool. We recommend that customers obtain a torque tester and check the tools frequently, and allow the results of the frequent checks to guide them as to the appropriate time for calibration. This best practice can avoid both under-calibrating the tools (tools out of specification being used) and over-calibrating (calibrating needlessly and incurring excessive downtime and expense).

For assistance in selecting the correct torque tester for this and for assistance in developing an appropriate process for your operation, please contact either the S/R Sales Department or your local S/R Representative.