How Much Torque Do I Need In An Impact Wrench?

An impact wrench is one of the handiest tools you can own. I got by with a breaker bar and a good socket set for years, but the day finally came when I needed to upgrade. Frankly, some repair tasks cannot be done without an air impact wrench.

And an air impact wrench speeds up how quickly you can work. Impact pneumatic wrenches produce from 30 to 3000Nm of torque.

As you shop for an impact wrench, you are undoubtedly wondering, “How Much Torque Do I Need For An Impact Wrench”? We answer that question here:

How Much Torque Do I Need For An Impact Wrench?

You need over 1,100 ft pounds of torque in an impact wrench for most automotive repair tasks.

For example, an Impact wrench will need around 500 ft-pounds of torque to remove lug nuts, which is the most common automotive task they are used for. However, if they were overtightened by the last shop to install them, you will need an even larger impact wrench to remove those lug nuts.

If you purchase an impact wrench with 1,100 ft-lbs or more torque, you will be able to handle nearly all automotive work.

Of course, when working on semi-trucks or in the rail industry, you may need an impact wrench capable of 1,600 foot-pounds or more of torque.

Ultimately, the amount of torque you need is dependent on the task you are doing. There is not a one-size-fits-all standard impact wrench torque. Instead, their torque ranges from 300-foot-pounds to 2,200-foot-pounds of maximum torque, depending on the model.

With the wrong choice, you’ll have a heavier tool than you need or an impact wrench that is too small.


Powering a Car With An Impact Wrench

YouTube video

I love watching these guys powering a car with a cordless impact wrench. It just goes to show how much power is in one of these. Imagine if they had done this experiment with a pneumatic wrench. That car would have flown!


What Is Torque?

Torque is a physics term used to describe the measure of a force that can cause an object to rotate around an axis.

Just as force can be measured in linear movement, it can also be measured in a circle, such as the torque produced by an impact wrench or engine.

An impact wrench uses torque to tighten or loosen bolts and lug nuts when rotating. However, the distinguishing factor of an impact wrench is that it has small internal hammers that drive an internal anvil.

This hammering creates micro shocks of intense torque that makes it possible to deliver seized and overtighten bolts.

Does Impact Wrench Size Matter?

You will quickly identify that larger impact wrenches produce more torque as you shop impact wrenches. The maximum tool torque produced by the drive size of your impact wrench will generally fit into one of these ranges:

  • 1-inch Drive: 1,475 to 2,145 foot-pounds
  • 3/4-inch Drive: 1,200 to 1,600 foot-pounds
  • 1/2-inch Drive: 650 to 1,295 foot-pounds
  • 3/8-inch Drive: 200 to 600 foot-pounds

1-Inch and 3/4-inch drive wrenches are generally used for heavier equipment, while 1/2-inch and 3/8-inch drive impact wrenches are for automotive use.

Cordless impact wrenches are the least powerful and will only produce about 600 foot-pounds of torque. A cordless impact wrench is more flexible and makes it easier to move around and work outside, but a pneumatic impact wrench is needed for more difficult tasks.

Is An Impact Wrench’s Torque Adjustable?

As with any tool, you won’t want to run your impact wrench at the max torque all of the time. Instead, you will want to choose a suitable working torque for the task at hand.

Some impact wrenches customizable torque that is controlled by a lever on the handle. However, you won’t have as much control over cheaper air impact wrenches. Instead, there are two other options:

  • Regulating Tool Pressure:  By purchasing an aftermarket tool regulator that plugs into the air hose between the compressor and the impact wrench. This gives you fine-tooth control of the airflow for your projects.
  • Regulating Line Pressure: Every air compressor has an air regulator. With some models, you can adjust the air regulator to produce more air in some cases. More air can then produce more torque output. The downside is that you may risk damaging the air compressor or the hand tool. However, you can turn the air pressure down with no risk.

Even if your impact wrench produces 1,000 or more foot-pounds of torque, you can use it for small tasks like tightening lug nuts. The key is to not sit on the nuts too long.

What Happens If You Apply Excess Torque On An Impact Wrench?

We’ve worked on some pretty stubborn projects. There is nothing more maddening than loosening a harmonic balancer on a failing engine and not having enough nut-busting torque to get the job done.

There is no harm done to your impact wrench by trying to loosen a nut that is too tight. Work on it in short 5-10 second bursts with plenty of wait time between events to keep the tool from overheating.

Conversely, If you apply too much torque to your project, you will likely damage nuts and break the bolt. Overtightening a lug nut, for example, will warp the brake rotors and damage the hub of your car.

How To Modify Your Impact Wrench To Increase Torque?

Manufacturers will have maximum torque settings on all of their wrenches. Adjusting the torque settings in this manner will void your warranty.

A better decision is to rent or buy a more powerful tool.

The only way to increase torque output on your wrench is to disassemble the impact wrench and enlarge the cylinder and exhaust ports with a grinder. You’ll also need to cut the gaskets to match the new port sizes.

This will increase the amount of airflow through these parts.

Of course, it also weakens them and introduces many irregularities.

It is more likely that you’ll destroy your impact wrench to increase the torque with a Dremel.


Frequently Asked Questions

How Much Torque Does An Impact Wrench Need To Remove Lug Nuts?

An impact wrench will need as little as 73 foot-pounds to loosen a lug nut. However, most automotive shops will choose a wrench capable of at least 300 ft-lbs of torque to remove wheel lugs.

How Much Torque Does An Electric Impact Wrench Have?

A cordless impact wrench will produce about 300 ft-lbs of torque, while a corded impact wrench can produce up to 500 ft-lbs of torque. Generally, they produce the required torque to work on lug nuts but are not good for larger fasteners.

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