Torque wrenches are generally divided into two categories: constant torque electric wrenches and constant torque manual wrenches.

Constant torque electric wrench, also known as torque adjustable electric wrench, is a kind of electric wrench. Its main feature is that the torque can be set and adjusted.


Electric wrenches are mainly used in the steel structure installation industry and are specially used to install high-strength bolts of steel structures. High-strength bolts are used to connect steel structure joints, usually in the form of bolt groups.
High-strength bolts can be divided into two types: torsional shear type and large hexagonal type. The national standard torsion shear-type high-strength bolts are M16, M20, M22, and M24, and now there are also non-national standards M27 and M30. The national standard large hexagonal high-strength bolts are M16, M20, M22, M24, M27, M30 and so on. Generally, the tightening of high-strength bolts must be initially tightened and then finally tightened, and each step requires strict torque. A constant torque wrench must be used for the initial and final tightening of the large hexagonal high-strength bolts.

Tightening operation of electric torque wrench:

The constant torque electric wrench can be used for both initial and final tightening. When using it, adjust its torque first, and then use it to fasten the bolts.

1. Before starting the main engine, install the reaction arm of the electric wrench and find the support point of the reaction arm. Adjust the square drive head of the wrench to match the square socket over the nut.

2. Manually adjust the control button on the LCD screen of the wrench, adjust the torque of the controller to the torque value required for tightening, and determine the forward and reverse directions of the electric wrench.

3. Press the start button and the wrench starts to work. When the reaction arm of the electric wrench is firmly supported (the fulcrum can be an adjacent bolt or other position that can be used as a fulcrum), the bolt starts to be tightened. When the torque of the bolt reaches the predetermined value, the wrench will automatically stop to complete the tightening work.

4.If the reaction arm and the support point are stuck too tightly and cannot be separated, adjust the forward and reverse switches to the reverse direction, and then move the trigger wrench to remove it.

Precautions for the operation of electric torque wrench:

1. The fastening of high-strength bolts should be carried out at least twice. The first time is the initial tightening. The minimum torque value of the initial tightening is not less than 40% of the torque value required for tightening. The second time is the final tightening. In order to make all the bolts in the bolt group evenly stressed, the initial tightening and final tightening should be performed in strict accordance with the tightening sequence. Operate symmetrically according to the “double-cross” shape.

2. Operate in strict accordance with the operating procedures of the electric torque wrench. The bolts that are initially screwed should be marked for confirmation to prevent bolts from being skipped. When installing the bolts, ensure that the friction surface should be in a dry state, and the final tightening torque must be carried out according to the requirements of the set value.

3. Due to the influence of external force, temperature change, vibration and other factors on the torque or pre-tightening force of the bolt, the final torque value produced each time is different, and the torque deviation is normal within ±5%.

4. For the electric wrench whose torque has been set, it can be rotated 30° from the pre-tightening of the bolt to the tightening. For the bolts that have reached the set torque, there is no need to use the wrench again, otherwise, the bolt torque will be increased, and the load of the bolt and the electric wrench will also increase, which will damage the bolt and the wrench.

5. Clean and replace grease regularly. Generally, after working 5000 times, it should be cleaned and refueled to prolong the service life.

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