How to choose the right torque wrench？

Choosing Different Types of Wrenches

Correctly tightening joints on the production line is a fundamental step in ensuring the quality of the assembly process.

Those who manage the tightening strategies to be adopted are not always clear about the selection and use of wrenches, whether electronic or mechanical.

There are different types of wrenches: click wrenches, slip wrenches, analog and electronic torque wrenches with torque or torque/angle measurement.

 

click-type torque wrench

Click wrench applies torque and clicks at a specific threshold, usually adjustable.

The click can occur within a range of a few degrees (high risk of over-tightening) to several tens of degrees.

Advantages:
🔹 Lightweight;
🔹 Inexpensive.

Disadvantages:
🔹 After the click point, torque continues to be applied, often resulting in over-tightening depending on the operator. Therefore, some people set a lower target value, but the final torque is still a direct result of the operator's action, not the calibration of the wrench.
🔹 The applied torque is affected by the specific handling of the wrench. Improper handling can alter the applied torque.
🔹 No rotation control during tightening (the operator may tighten the same screw twice, or the bolt threads may seize, giving a false sense of tightness).
🔹 Torque cannot be measured or traced.

 

slip-type torque wrench

A slip wrench applies torque and slips at a certain threshold, usually adjustable. After slipping, the torque is completely released. If rotation continues, torque will be applied again.

Advantages:
🔹 Lightweight;
🔹 Inexpensive;
🔹 Eliminates the risk of over-torquing.

Disadvantages:
🔹 Only used for low torque. Some models can provide torque values up to 100 Nm or slightly higher, which already presents issues for operators when the torque is suddenly released;
🔹 Because the wrench acts on different mechanical teeth, each slip point has a distinct torque value;
🔹 The applied torque is affected by the specific handling of the wrench. Improper handling can alter the applied torque;
🔹 No rotation control during tightening (the operator may tighten the same screw twice, or the bolt threads may seize, giving a false sense of tightness);
🔹 Torque cannot be measured or traced.

 

Dial torque wrench

Analog dial torque wrench provides real-time torque readings.

Advantages:
🔹 Lightweight;
🔹 Inexpensive;
🔹 Provides an estimated torque.

Disadvantages:
🔹 The final torque depends on the operator's stopping point. Therefore, even if the wrench is fully calibrated, tightening repeatability cannot be guaranteed;
🔹 The applied torque is affected by specific handling. Improper handling can alter the applied torque;
🔹 The wrench cannot be programmed for the tightening to be performed and does not provide operators with guidance for correct tightening;
🔹 No rotation control during tightening (the operator may tighten the same screw twice, or the bolt threads may seize, giving a false sense of tightness);
🔹 Torque cannot be measured or traced.

 

Modern electronic torque wrenches can provide torque readings and, if equipped with a gyroscope, can also provide angle readings.

Advantages:
🔹 Torque and angle control for "certified" correct tightening;
🔹 The wrench displays torque and parameters;
🔹 Tightening results are reported to the operator in real time;
🔹 Programmable tightening strategies;
🔹 Perform tightening and quality control tests (residual torque control);
🔹 Ability to control tightening extensions in confined spaces;
🔹 Torque measurement is independent of handling (if the wrench is equipped with a dual-bridge sensor);
🔹 Data traceability;
🔹 The wrench can be used as a backup fastening tool on the assembly line.

Disadvantages:
• More expensive than conventional torque wrenches;
• May be heavier than conventional torque wrenches.

 

How to Choose a Digital Torque Wrench for Production or Quality Control?

 

A quality control wrench must be equipped with:
🔹 Torque sensor and gyroscope;
🔹 A large display showing tightening parameters;
🔹 On-screen tracking curves.

For quality control, the same wrench can also be used to perform production tightening operations (if equipped with a production tightening strategy), or a more streamlined digital torque wrench can be used. This streamlined version is equipped only for tightening operations, providing the operator with a simplified wrench featuring LEDs and a lever, combined with a remote control panel.

A digital torque wrench for production must be equipped with:
🔹 Torque sensor and gyroscope;
🔹 LED/buzzer/vibration device to provide real-time feedback to the operator;
🔹 Association of the production workpiece serial number with the test;
🔹 Data traceability communication with software and database.