What is an Impact Wrench?

Removing fasteners can be a nightmare. If you’ve ever had to change a flat tire, you know how difficult it can be to remove a rusted-on lug nut. Now imagine yourself as an auto mechanic, having to repeat this process dozens of times every day.

As you can see, it can get pretty strenuous after a while. Not only does this repeated strain slow down workflow, but it can also lead to injuries over time. Professional mechanics needed an easier way to effectively “break” these tough bolts.

Impact wrenches were created to help solve this problem.
When most people first see an impact wrench, they often make the mistake of assuming it’s some sort of drill. But it’s a completely different, very specialized tool.

This combination of speed and power is also why pit crew use them to change race car tires. When every second counts, impact wrenches get the job done.

What are they used for?

In reality, impact wrenches are really more of a faster, more powerful substitute for a ratchet.

Most commonly used with cars and machinery for removing/installing bolts, impact wrenches help you get more work done in shorter time. These tools are essential since maximizing productivity is the key to increasing profitability.

How do they work?

The first time you use one, it can feel a bit intimidating. Impact wrenches are loud, scary and they kick. The secret to their effectiveness is the sudden, violent acceleration force delivered by the rotating head. (Also called the “anvil”)
Designed to deliver the maximum amount of torque with the least amount of effort by the user, it accomplishes this rotating a free-spinning hammer inside the device. As it picks up momentum and reaches maximum speed, the hammer then collides with the anvil on the inside of the device and causes the head to rotate.

After hitting the anvil, the hammer is released and continues spinning until it comes back around to collide again and again.

The power that would normally be delivered in 1/10 of a second is instead delivered in just 1/100 of a second, causing a multiplication of force that is delivered through the socket head and into the stuck fastener.

Thanks to Newton’s first and second laws of motion, the combined with the weight and acceleration of the tool also means that less energy is transferred to the operator. This is the same principle that allows you to yank out a tablecloth without spilling your food on the floor.



If you tried doing the same thing with a normal drill, you would have to fight hard against the machine as it spins. I won’t go too deep into it, but there are a lot of great physics web sites out there that discuss the science inertia in more detail.

When it comes to impact wrenches, you want to find one that delivers the greatest impact in the shortest space of time. Compressed air is great for this because it gives greater power output for better torque. With electrical units, you’re limited to household wattage, or battery power. (Hydraulic wrenches are also available, but they’re also less practical for most common applications)

If you find yourself struggling with stuck fasteners, you may want to consider looking into a compressed air impact wrench for your shop.