How Does an Air Impact Wrench Works

How Does an Air Impact Wrench Works?

Nuts can often be too tightly wounded when you can’t turn them with regular wrenches. Even if the nut head is stripped, you might not catch the nut in some cases. An air impact wrench is a right tool to deal with such nuts.

No matter how tight or stripped the nut is, you can turn them with strong enough torque in short bursts. Such a wrench consists of several different parts. In this article, we will take a look at the inside of an air impact wrench and find out how does an air impact wrench works.

Let’s start twisting.

What is an Air Impact Wrench?

An air impact wrench is a pneumatic tool that produces high torque to have a short but consistent impact on the nut. The intensity of the rotating force in an air impact wrench is high enough to rotate a lug nut.

work with an air impact wrench
Air Impact Wrench

This machine is also known by other names like air wrench, rattle gun, or torque gun. Air impact wrenches are commonly used in heavy industries to assemble or disassemble different components.

Impact wrenches run mostly on compressed air or electricity. The wrenches running on compressed air are known as air impact wrenches. They are also known as pneumatic wrenches.

Air impact wrenches are popular among professionals for their high torque delivery. From the automobile to the aerospace industry, an air impact wrench has its usability everywhere. Before we get to know how it works, let’s take a closer look at the parts of this machine.

Components of an Air Impact Wrench

Though there are many small parts in an air impact wrench like a cage pin or hammer gasket, we will focus on major components.

  • Wrench Housing
  • Hammer
  • Rotor
  • Rotor Blade
  • Cylinder
  • Output Shaft
  • Trigger

How Does an Air Impact Wrench Work?

To be simple, the working principle of air impact wrenches is to rotate the hammer and hit the output shaft with a strong force to create high torque. The rotor turns the hammer, compressing the spring behind it.

air impact wrench working mechanism
Air Impact Wrench Working Mechanism

Once the hammer reaches the edge of the output shaft, the energy conserved in the spring comes into action and makes the hammer hit the output shaft again.

Thus, a constant impact on the output shaft is created, which helps to loosen or tighten nuts easily.

Let’s break the steps down to make you understand better.

Air Flow into the Wrench

Air Impact Wrench

You need an air compressor to run impact wrenches. Compressed air enters the housing through the base of the machine.

This compressed air is used to turn the rotor blades. As a result, the main rotor turns to rotate the hammer.

Jerking Motion of the Hammer

The hammer in an air impact wrench is specially designed with several teeth. It can rotate and slide along the shaft axis simultaneously. There is a spring at the back of the hammer.

When rotating, the teeth of the hammer hit the output shaft once or twice per rotation. The impact of the teeth of the output shaft sustains for a short period but generates enough torque to rotate nuts.

Spring Compression

There are steel balls between the hammer and the output shaft. The steel balls push the hammer to compress the spring. In this state, the spring gains some energy to push the hammer forward again.

Once the locked tooth of the hammer passes the edge of the output shaft, the hammer is pushed by the spring to hit the output shaft again. This results in a constant, forward impact on the output shaft.

If there is no load on the wrench, the output shaft will run smoothly without this jerking motion, just like a simple pneumatic drill.

Benefits of Air Impact Wrench

An air impact wrench can benefit you in many ways. Here are a few of them.

  • Using an air impact wrench is much more efficient than using muscle power to loosen or tighten nuts. Especially when the nuts are tightened with machines, loosening them with muscle power is very difficult. An air impact wrench will come in handy in such cases.
  • If you have a lot of nuts or bolts to tighten or loosen, air impact wrenches will get the job done much faster than doing them by your hands. This is beneficial when you are working on the industrial level, for example, in a car production line.
  • Air impact wrenches are very easy to use. You don’t need much technical knowledge to use them.
  • These wrenches have fewer moving parts than other types. So, less maintenance is required for these tools. They also remain very durable for a longer period.
  • Running air impact wrenches only require compressed air. This is a lot cheaper than running electric impact wrenches.


Know the answer to some frequently asked questions here.

Q. How Powerful is an Air Impact Wrench?

Ans. Power refers to the torque generated by the impact wrench here. Most models can generate 1000-1500 pound-feet of torque.

Q. What Size Air Compressor is Needed for an Air Impact Wrench?

Ans. This depends on the size and power of the impact wrench you are using. Using an impact wrench with a 1/2-inch drive will require an air compressor that can deliver 4-5 CFM at 90 PSI. If the drive is 1 inch, you need an air compressor that can deliver 10 CFM.

Q. How Much Torque is Required to Loosen Lug Nuts?

Ans. You will require at least 100 pound-feet of torque to loosen lug nuts.


Air impact wrenches are extremely useful for handling lug nuts, and assembling or disassembling a large number of nuts.

Their constant impact brings motion to the nut when it is quite impossible to tighten or loosen the nuts with your hand. And when there is no hindrance, air impact wrenches will make the job faster.

Knowing how an air impact wrench works will enlighten you on the components and working principles of this machine. Don’t sweat lug nuts from the next time. Get an air impact wrench to finish the job with increased efficiency.

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