How to choose the right torque wrench for the job
A torque wrench tightens fasteners to a precisely defined value so the joint reaches the correct preload. This guide explains how to pick the measuring range in Nm, when click or digital technology pays off and what calibration to DIN EN ISO 6789 means.
View torque wrenchesWhich measuring range in Nm do you need?
The required torque follows from bolt size, property class and the manufacturer specification for the joint. Choose the wrench so the target value sits in the middle of the scale, because that is where click wrenches are most accurate.
As a rule of thumb the set torque should fall between 20 % and 80 % of the range. A 40‑200 Nm wrench suits values around 80‑160 Nm well, but would be too coarse and imprecise for 15 Nm.
Click or digital - which release type fits?
Click torque wrenches give a noticeable and audible click when the set value is reached. Digital wrenches measure electronically and signal the target torque through display, LED and sound, often with memory and angle measurement.
- Click (mechanical): rugged, low maintenance, no power needed, ideal for repeated identical values.
- Digital (electronic): value set freely on the display, peak and track modes, logging possible.
- Digital with angle measurement: for the torque-angle method to manufacturer specification.
- Preset versus scale-adjustable: for fixed values in series assembly the preset type pays off.
What does calibration to DIN EN ISO 6789 mean?
DIN EN ISO 6789 defines requirements and test methods for hand-operated torque tools. It distinguishes Type I (indicating) from Type II (setting, e.g. click wrenches) and fixes the permitted deviation and the calibration procedure.
For setting wrenches a tolerance of ±4 % of the set value usually applies. Calibration is done at several points across the range and documented in a certificate that proves traceability to national standards.
- Recalibration typically after 12 months or about 5000 releases.
- Return a click wrench to the lowest scale value after use to relieve the spring.
- Do not use it as a loosening or striking tool, this corrupts the calibration.
- Keep the calibration certificate and test date, especially where proof is required.
Frequently asked questions
In which part of the scale is a click wrench most accurate?
In the middle range, roughly between 20 % and 80 % of the measuring range. Values near the low or high end are less accurate, so keep the target off the edge of the scale.
How often must a torque wrench be calibrated?
Common practice is recalibration after about 12 months or around 5000 releases, whichever comes first. With intensive or proof-required use, do it more often.
Why turn a click wrench back down after use?
Returning it to the lowest value relieves the release spring. This keeps the set accuracy more stable over the tool life.
What is the difference between Type I and Type II under ISO 6789?
Type I are indicating tools that show the torque on a scale or display. Type II are setting tools such as click wrenches that give a signal at the target value.
Looking for the right torque wrench?
We supply click and digital torque wrenches for every range - calibrated and tested to DIN EN ISO 6789.
Standard tested
Calibration to DIN EN ISO 6789 with certificate.
Precise
Release accuracy down to ±2 % of the set value.
Traceable
Calibration certificate referenced to national standards.
Expert advice
Our specialists help with range and type.