Why torque wrenches are checked
Wheel bolts, cylinder head, suspension, brakes: wherever the manufacturer specifies a tightening torque, safety depends on the right value. A torque wrench loses accuracy over time – the spring tires, the mechanism wears, a fall or an overload knocks it out of adjustment without anyone seeing it.
That is why the torque wrench is the best-known piece of test equipment in the car repair workshop. How test equipment is monitored in general is described in the guide Test equipment management in the workshop. This guide is about the torque wrench in particular.
Which intervals apply
The standard ISO 6789 recommends recalibrating a torque wrench, unless otherwise specified, after 12 months or 5,000 operations – whichever comes first. Shorter intervals may be set by:
- the vehicle manufacturer or importer in its workshop standards,
- your own quality management,
- the manufacturer of the wrench.
Regardless of the interval, a wrench must be checked at once if it has been dropped, overloaded or repaired, or if it releases unusually.
Checking, calibrating, adjusting
The three terms are often confused:
- Checking: it is established whether the wrench lies within the permitted deviation. Depending on type and class, the standard usually allows 4 or 6 percent.
- Calibrating: the deviation is measured with a traceable instrument and documented in the calibration certificate – with measured values, not just "OK".
- Adjusting: if the wrench is outside the tolerance, it is adjusted or repaired. Afterwards it is calibrated again.
What counts for the workshop in the end is the proof: a calibration certificate with date, measured values and the wrench's identifier.
Factory certificate or accredited calibration certificate
A certificate from an accredited calibration laboratory – in Germany accredited by DAkkS – is recognised internationally and is explicitly required in some audits. A factory calibration certificate from the manufacturer or a calibration service is usually cheaper and is enough for many workshops. Which one you need is set out in the requirements of the manufacturer and your quality management – if in doubt, clarify before ordering.
Checking it yourself with a tester
With your own torque tester you can check in between whether a wrench is still accurate – after a fall, for example. The tester itself must be calibrated regularly. Such a check does not replace calibration if the manufacturer or quality management requires a calibration certificate.
Storing and using it correctly
- After work, turn click-type wrenches back to the lowest value on the scale, not below it – so the spring is not permanently under tension.
- Do not use it to loosen tight bolts and do not fit an extension.
- Store it in its case, not loose in the tool trolley.
- Report every fall instead of quietly carrying on.
Test dates without downtime
A torque wrench that is at the calibration service is missing in the workshop. Proven practice:
- Advance warning 30 days before, so the date can be planned.
- A joint date for several wrenches – many services collect and return.
- Plan a replacement for measuring ranges needed every day.
- Know who has the wrench before the date – otherwise it is missing at collection.
Frequently asked questions
Is it enough to have a torque wrench checked once a year?
Unless otherwise specified, yes: ISO 6789 recommends 12 months or 5,000 operations, whichever comes first. If a wrench is used very often or the manufacturer specifies shorter intervals, the shorter interval applies.
Does a torque wrench that has been dropped need recalibrating?
It should be checked before it is used again. A fall can knock the mechanism out of adjustment without anyone seeing it. Until the check, the wrench is blocked and no longer issued.
May a workshop calibrate its torque wrenches itself?
With a calibrated tester it can check them itself and document the result. Whether this in-house check is enough as proof or a certificate from a laboratory is needed is decided by the vehicle manufacturer and your quality management.
How it works with Tulz
In Tulz every torque wrench gets an inspection interval – preset for the whole category, changeable per wrench. Inspections that are due appear on the advance warning list 30 days ahead and arrive by email. The inspection record stores the result, measured values and the calibration certificate as a file, an interval can be postponed with a reason, and when issuing, Tulz points out expired inspections. Who has the wrench right now is shown on the tool page.
Guides in the help centre: Inspections · Correct an inspection · Test equipment note when issuing · Documents