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How does an impact wrench work?


Impact wrench is a high-torque tool designed to ease strenuous tasks. It's a staple in professional mechanics' kits and DIY enthusiasts' toolboxes, making hefty tasks like tightening lug nuts or assembling furniture swift and efficient.

This powerful tool is not just limited to personal use; it holds significant importance across various industries. Impact wrenches work great for tightening and loosening bolts, lug nuts and rusted fasteners. They provide a high rotational torque that regular drills are incapable of and provide high torque output with minimum effort from the user.

They are commonly used in the automotive and construction industries, although they are favored in many other trades requiring high torque output. 

Having introduced the impact wrench, let's delve deeper and explore the mechanics of how impact wrench works. Let’s get started.


Main components of an impact wrench

An impact wrench is a complex tool, each part of this plays a critical role in its operation. Understanding its components can help you appreciate the engineering behind it. Here are the main parts of an impact wrench:

  • Motor: The motor is the heart of an impact wrench. It's either electric or pneumatic, depending on the type of wrench. The motor provides the power needed to drive the hammer mechanism.

  • Hammer mechanism: This is where the real magic happens. The motor powers the hammer mechanism, making it rotate. As it rotates, it hits the anvil, creating a high-torque impact which is then transferred to the output shaft.

  • Anvil: The anvil is hit by the hammer mechanism. The force from this impact is what creates the high torque that makes an impact wrench so useful.

  • Output shaft: The output shaft, also known as the drive, is the part of the wrench that interfaces with the socket. The high-torque force from the anvil is transferred to the output shaft, which turns the socket and allows for the tightening or loosening of nuts and bolts.

  • Trigger: The trigger is the control mechanism of the impact wrench. When pressed, it activates the motor, which in turn drives the hammer mechanism.

  • Reverse switch: This switch allows the user to change the direction of the output shaft, enabling them to either tighten or loosen nuts and bolts.

  • Battery (for cordless models): Cordless impact wrenches are powered by rechargeable batteries. These batteries provide the energy needed for the motor to function.

How does an impact wrench work?

An impact wrench has an air motor or electric that applies a sudden, intense rotational motion to the retentive lug nut, usually in short bursts (every five seconds or so). Continuous short, intense bursts of force trying to turn the fastener eventually lead to some movement (loosening or tightening). 

The pressure pushes the fastener forward in addition to adding more force to improve the impact wrench's torque. This process helps the impact wrench do a much better job on the fastener than you could ever hope to do by hand.

Electric/Cordless impact wrenches

Motor operation: Just as a heart pumps blood through our body, the motor in an electric impact wrench drives the entire operation. The battery supplies power to the motor which then converts it into rotational motion. The motor's function is akin to a windmill turning in the breeze.

Impact mechanism functioning: This rotational motion is transferred to the hammer mechanism. Imagine a child on a swing - the more you push (or the more power the motor provides), the higher the swing (or the hammer) goes. When the swing comes back down, it does so with force. Similarly, the rotating hammer hits the anvil, generating a powerful impact that's transferred to the output shaft.

Pneumatic impact wrenches

Air motor functioning: Pneumatic impact wrenches use an air motor instead of an electric one. Picture a sailboat - the wind (or in this case, compressed air) fills the sails (the vanes of the air motor), propelling the boat (or the wrench) forward.

Impact mechanism working: The working of the impact mechanism in a pneumatic impact wrench is similar to that in an electric one. The air motor powers the hammer mechanism which strikes the anvil, creating a high-torque impact.

As mentioned above, impact wrenches are usually powered by either air (a pneumatic impact wrench) or electricity. A pneumatic impact wrench can deliver the highest torque and is generally considered the most professional grade impact wrench. However, an electric impact wrench can provide enough punch to do the average do-it-yourself-er.

Benefits of using an impact wrench

High torque output: An impact wrench produces a high level of torque, which is the force that causes rotation. Imagine the power of a whirlwind, able to spin objects with immense force. That's the kind of strength you can expect from an impact wrench.

Less Effort Required by the User: Using an impact wrench requires minimal effort. Just point, press, and watch the tool do its magic.

Effective on tight or rusty bolts: If you've ever tried to loosen a rusty bolt, you know it can be as stubborn as a mule. But with an impact wrench, it's like having a master negotiator persuade the bolt to move.

Versatility: An impact wrench is not a one-trick pony. It can be used in a variety of applications, from automotive repair to construction and more. Think of it as a swiss army knife of power tools.

When to use an impact wrench?

You should probably know when to use an impact wrench. They are helpful in any application that requires more power or when a hand wrench won't work.


  • Automotive repair: In the automotive industry, impact wrenches are indispensable. Anytime while dealing with tough bolts and nuts, like a 10mm bolt rusted on a car, or your tire nuts, you'll want to get out the impact wrench. They're used for tasks like removing lug nuts from tires or bolts from engine parts with ease and precision. 

  • Construction: Construction sites often require the assembly and disassembly of various components. Anytime you need a hand wrench is an excellent time to use an impact wrench. An impact wrench proves invaluable in such settings, providing the high torque needed to drive screws into hard materials like concrete or steel, or to quickly dismantle structures.

  • Manufacturing: Precision and speed are key in the manufacturing industry. Whether it's assembling machinery or maintaining equipment, an impact wrench ensures tasks are done accurately and efficiently. Many impact wrenches have three speeds. You can change your impact wrench's power level for a particular work.

  • Other industries: The versatility of impact wrenches extends to many other industries as well. They're used in everything from oil rigs to aerospace engineering, making them a staple in any heavy-duty toolkit.

Safety considerations when using an impact wrench

Remember, safety is paramount when using power tools. Following these precautions will help ensure a safe and productive work environment. When used under the right conditions and with care, the impact wrench will save you a lot of time and effort on each task.

  • Wear proper safety gear: Impact wrench can propel materials such as metal chips, sawdust and other debris at high speeds, which can result in serious eye injury. Long-term exposure to noise generated by power tools can cause permanent hearing loss. It's essential to don the right protective equipment when using an impact wrench. This includes safety glasses to protect your eyes from flying debris, gloves to ensure a secure grip, and ear protection to shield against noise. 

  • Be aware of your surroundings: Keep a keen eye on your environment. Make sure there are no tripping hazards or loose materials that could cause accidents. Besides, never wear loose clothing or jewelry while using this. 

  • Use the correct socket for the bolt size: Always match the socket size to the bolt you're working on. Using the wrong size can lead to striping of the bolt head or even breakage.  Impact sockets are often distinguished from regular sockets by their thick walls and flat black appearance due to their hardening process.

  • Do not overtighten bolts: Over-tightening bolts can cause them to break or strip, leading to damage and potential injury.

  • Inspect the impact wrench and accessories for damage: You should never use damaged tools or accessories; This can result in serious injuries. Before using an impact wrench, inspect the device for any cracks, breaks or other signs of damage. Replace or repair any damaged equipment.


The complex mechanics of the impact wrench combine to create a powerful and efficient tool that has revolutionized how we tackle various projects. 

To summarize, an impact wrench works by transforming power into high-torque action. It tackles stubborn bolts, saves time, and reduces manual labor. Its versatility spans across automotive repair, construction, manufacturing, and other industries, providing an efficient solution to many operational challenges.

Explore BISON range of impact wrenches

BISON impact wrenches stand at the intersection of power and precision. Each tool is designed to deliver high-torque action. It's time to elevate your inventory with our top-tier impact wrenches.

We invite you to explore our extensive range of impact wrenches. Experience the synergy of power, precision, and performance that each of our tools provides.

For more information or to discuss dealership opportunities, contact us at [email protected] or call us at +86 136 2576 7514. Enhance your product range, satisfy your customers, and drive your business growth with our superior impact wrenches. Act now!


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