A pneumatic torque wrench is a torque multiplier that drives and outputs torque through high-pressure air to tighten/remove nuts and bolts. It is very important and widely used in manufacturing and assembly lines, construction and engineering projects, aerospace and other fields. It is one of the important torque tools for tightening or disassembling high-strength, large bolts and nuts.

In this article, TorcStark will introduce the working principle of the pneumatic torque wrench in detail, hoping to help you use and understand it better.

Components of Pneumatic Torque Wrench

1. Compressed air or nitrogen drive:

The power source of the pneumatic wrench is compressed air or nitrogen. Before use, the air source needs to be connected to the pneumatic wrench, and compressed air or nitrogen is stored in the air chamber inside the wrench to generate a certain pressure. When you need to use a pneumatic wrench, you only need to open the valve and conduct the air pressure to the pushing device to generate pneumatic force.

2. Pneumatic motor:

There is a pneumatic motor inside the pneumatic torque wrench, which is used to convert the pressure of the air source into rotational force. The high-pressure compressed air blows the motor blades to rotate the motor rotor, and outputs rotational motion to the outside. Air motors usually use a turbine or gear mechanism to transfer the rotational force driven by air pressure to the output shaft.

3. Gear set part:

It consists of three or more layers of epicyclic gears. It mainly amplifies or reduces the rotational motion output by the pneumatic motor and outputs it to the work head, thereby achieving changes in torque and rotation of fasteners.

4. Torque sensor:

To achieve precise torque control, the pneumatic torque wrench is equipped with a torque sensor inside. The sensor measures the amount of torque on the output shaft and communicates this information to the control system.

5. Control system:

The control system of the pneumatic torque wrench is the core of the entire tool. It achieves precise torque control by adjusting the pressure of the air source based on the preset torque value and current torque sensor feedback. The control system generally includes a pressure regulator, electronic control unit and display screen.

6. Air filtration and air pressure adjustment part:

Since compressed air is usually transported through pipelines made of seamless steel pipes, during long-term use, corrosion on the inner wall, moisture and dust in the compressed air will continue to form. Suppose such compressed air enters the pneumatic motor directly without any treatment. In that case, the life of the motor will be greatly shortened, resulting in insufficient and unstable power output of the entire tool, which may easily cause serial damage to the motor and other parts. Therefore, a compressed air filtering and regulating device must be installed between the compressed air transported by pipelines and the pneumatic tools, and the pneumatic triplex assumes this task. Pneumatic triple parts are mainly composed of air pressure gauges, filters, lubricators, pressure regulators and other parts. The filter has a built-in filter element, which needs to be maintained, cleaned and replaced regularly after being used for some time.

7. Tool accessories:

Reaction arm, snap ring that fixes the connection between the reaction arm and the wrench, air pipe, pressure gauge, filter, regulator, and oil injector triple set of tools.

Working principle of pneumatic torque wrench

Through the above introduction of the components of the pneumatic torque wrench, it can be concluded that the basic working principle of the pneumatic torque wrench is as follows

The working principle of the pneumatic torque wrench is based on the air compressor generating high-pressure gas, which is transmitted to the turbine rotor inside the torque wrench through the pneumatic device, causing it to rotate. Then it is converted into torque output through the reduction mechanism, thereby achieving the purpose of disassembling and assembling bolts, screws and other fasteners.

When using a pneumatic torque wrench, the operator first connects the tool’s output shaft to the bolt or nut to be torqued and sets the required torque value.

Then, when the operator starts the pneumatic torque wrench, the air source begins to provide compressed air, which generates rotational force through the pneumatic motor.

The torque sensor monitors the torque on the output shaft in real-time and sends feedback signals to the control system.

The control system automatically adjusts the pressure of the air source based on the feedback signal and the preset torque value to keep the torque on the output shaft constant.

When the output shaft reaches the preset torque value, the pneumatic torque wrench will automatically stop rotating to avoid over-tightening.

Advantages and Disadvantages of Pneumatic Torque Wrenches


1. Efficient: Pneumatic torque wrenches use air pressure as the power source, and their torque output is more efficient than ordinary wrenches, and it only takes a short period of time to reach the required torque value.

2. Precision: Since the turbine rotor drives the output of the pneumatic torque wrench, its torque output is more accurate, and precise control of the torque can be achieved by adjusting the air pressure and air volume. Pneumatic torque wrench equipped with sensor and solenoid valve switch, with repeatability up to ±2%.

3. Reliable: Due to the simple design of the pneumatic torque wrench and the materials used are high-strength alloy steel, its service life is longer than that of the electric torque wrench, and its durability and stability are higher. There is no significant noise or impact during operation, which reduces damage to tools, sleeves and locked objects. No pollution, low cost of use, comfortable and safe for long-term use.

4. Wide range of applications: In addition to being used for disassembly and assembly of fasteners, pneumatic torque wrenches can also be widely used in the maintenance of various mechanical equipment, such as automobiles, aircraft, ships, etc.


1. Reliance on compressed air: It is difficult to obtain compressed air, and many complex working environments or long-distance working environments prevent the use of pneumatic torque wrenches.

2. Complexity: Air torque wrenches are made up of complex internal components, and failure to properly maintain these tools can result in reduced efficiency, increased downtime and higher repair costs.

3. Air Quality and Contamination: Contaminants such as moisture, oil, and debris present in compressed air can damage the internal components of the torque wrench, resulting in reduced efficiency and potential failure.

Maintenance and safety precautions for pneumatic torque wrenches

Routine maintenance:

1. After working continuously for 3 to 4 hours. Separate the tool from the air source, drip 7-8 drops of high-purity light engine oil (low viscosity) from the air inlet of the tool, then connect the air pipe, open the air source, and blow the oil into the cylinder. Users who have the conditions and work at full load are recommended to install a small oil injector at the air inlet joint.

2. Usually, the air compressor and oil-water separator need to be regularly drained and impurities removed every 30-40 days to ensure that the air entering the tool is clean and dry.

Safety Precautions

1. To ensure the accuracy of torque output, before using a pneumatic torque wrench, you need to select the appropriate bolts and air pressure according to the type and specifications of the fasteners to be disassembled, otherwise, the torque output may be inaccurate.

2. When using a pneumatic torque wrench, you need to pay attention to safety precautions to prevent the wrench from sliding or rebounding.

3. During long-term or high-intensity use, proper lubrication and maintenance are required to extend the service life of the pneumatic torque wrench.

3. Drain the accumulated water in the three-point control valve regularly.

4. The air outlet filter cotton of the pneumatic torque wrench body needs to be cleaned twice a week.

5. The interior of the pneumatic torque wrench body should be maintained at least once every six months.

6. If further maintenance is required, do not disassemble the transmission part by yourself. It is recommended to contact the sales unit.

7. Regularly calibrate the air pressure gauge and the air pressure-torque relationship to ensure that it meets the working requirements. Please contact the sales unit.

In the end

Through the above introduction, I believe you have a deep understanding of the composition, working principle, advantages and disadvantages, and maintenance of pneumatic torque wrenches. Therefore, TorcStark recommends that you follow correct operation and maintenance methods when using your pneumatic torque wrench to ensure the best experience and performance.