Excellent performance level of 1,350 foot-pounds of torque that can handle most jobs. Extremely tough materials in the device. Offers 4 power settings to adjust torque. Easy-to-use forward and reverse button. Minimal vibration during use will prevent you from feeling fatigued. Runs quieter than you'd think.
Some questions over longevity if you're going to use it all day long on really tough jobs.
Offers 2 power settings that are convenient to adjust on the fly. Easy to switch between forward and reverse functions. Good value for the price. Runs more quietly than most air impact wrenches. Will work well with a smaller air compressor. Nice entry-level tool for basic jobs, because it doesn't really offer torque for tough jobs.
Limited to 600 foot-pounds of torque. Heavier gun that may cause fatigue over time.
Includes adjustable power regulator. Placement of forward and reverse switch means it can be operated with one hand. Maximum torque of 650 foot-pounds, which provides enough power for most jobs around the home. Feels well balanced when you're using it. Offers 3 preset power levels.
Requires plenty of air pressure to work. Won't perform as well on heavy-duty jobs.
Handle features an ergonomic design that helps prevent fatigue in the wrists and forearms while using it. Air exhaust routes through bottom of handle to keep it out of operator's face. Offers an impressive 1,295 foot-pounds of torque. Surprising amount of power considering how quietly it operates.
May not stand up to tough conditions during continuous use, eventually breaking down.
Fast-performing air impact wrench that runs at 10,000 RPM. Small body that's easy to handle in tight spaces. Tool's design modeled after NASCAR racing pit crew tools. Heavy tool that feels solidly built while you're using it. Works well for most jobs around the home, but it doesn't have torque needed for heavy-duty jobs.
Limited to 550 foot-pounds of forward torque. Price is above average.
We purchase every product we review with our own funds — we never accept anything from product manufacturers.
We purchase every product we review with our own funds — we never accept anything from product manufacturers.
Air impact wrenches have been the professional's tool of choice for everything from changing tires to building ships for over 60 years. These tools are powerful, reliable, durable, and easy to maintain. Many modern air impact wrenches are both more compact and more affordable than the full-on pro models, which makes them a popular choice with home mechanics.
BestReviews has been assessing the capabilities of a wide range of these tools. Our recommendations encompass everything from entry-level air impact wrenches to top-of-the-line models. There's something there for every need and budget. We've also put together the following air impact wrench buying guide, which delves into all the details you need to consider when buying.
How an air impact wrench works
An air impact wrench (also known as an air gun, impact gun, or impactor) has a simple job: to loosen or tighten nuts and bolts. The advantage it has over an ordinary wrench is the amount of torque (twisting force) it applies.
Power is supplied either by an electric motor in the impact wrench or by air from a compressor. Unlike a drill, which delivers constant rotational force, the impact wrench delivers a series of rapid strikes with short pauses – these “impacts” jar a bolt or nut loose. It's a bit like hitting your standard wrench with a hammer but much more effective.
Electric vs. air
Electric: Electric impact wrenches are common among nonprofessional users because all you need is a convenient outlet and away you go. Cordless models are increasingly popular because they can go anywhere, and improvements in battery power mean there's less of a performance disadvantage than before. However, prices remain high, and run/recharging times can still be frustrating.
Air: The drive in an air impact wrench is a much simpler than the motor in an electric model, which makes the tool easier to maintain and less prone to failure. It's not unusual for one to last decades. Air impact wrenches are also quite a lot lighter, which makes a big difference if you're using one for long periods, and considerably cheaper, though there is the cost of a compressor to consider.
Air impact wrenches often produce more torque than electric models, too. In the past, these tools had little or no control and were criticized for being too powerful for home use. Fortunately, that's no longer the case. The variety of tools available and the controls provided mean you have the same versatility as you do from electric tools.
All that said, an air impact wrench is not for everyone. If you're constantly moving from one place to another, the alternatives are more convenient. However, if you usually work in the same garage or workshop, these tools have some impressive advantages.
Torque: You'll often see two torque figures: nut-busting (also called breakaway) torque and maximum torque, given in foot-pounds (ft-lbs.). The former is invariably the headline number and suggests that a higher torque is available for loosening difficult nuts. That may be true, but unfortunately there's no industry standard for measuring it. In truth, it's a bit of a marketing gimmick, so if actual torque output is important to you, focus on maximum torque.
You don't necessarily want the air impact wrench with the highest torque rating. You need the one that matches the tasks you have to perform. That could mean 250 ft-lbs. is sufficient. You don't always need 1,000 ft-lbs.
Settings: You can alter the torque output on good air impact wrenches. Sometimes this is a single reverse setting – because you just need to get the nut off – plus two or three forward settings, which reduces the risk of overtightening. Top-end machines have three reverse and three forward.
Beats per minute: You'll usually find the beats or blows per minute (bpm), which is the speed of the impact action. It's not of major importance, but if you've got two very similar tools, a faster BPM is preferred.
Rotations per minute: You may also find rotations per minute (rpm), or free speed, quoted. Again, it's a secondary figure that tells you how fast the wrench can rotate while removing or attaching a fixing, but it has no bearing on the torque.
Anvil: Impact sockets attach via a square drive called an anvil. On electric models, this can be 1/4, 3/8, or 1/2 inch, but on-air impact wrenches it's usually 1/2 inch because, in general, it is transmitting more power, so you want a larger contact area.
There are two types of anvil: hog ring (friction fit, which is very fast) and detent pin (bearings provide a click fit, which is slightly more secure). In practical terms, there's little difference, although professionals tend to prefer speed.
Materials: Cheap air impact wrenches often have plastic body moldings. A rubberized grip is useful to give you a good grip, but other parts should be metal or tough composites. These tools are often poorly treated, so they need to be ruggedly built.
Hose: Be sure to check the hose size and that the connectors are compatible, particularly if you already have a compressor.
It's important to have a compressor that can supply sufficient air for your impact wrench. Air tools and compressors have two ratings: Maximum air pressure is measured in pounds per square inch (psi), and the airflow supplied or required is measured in cubic feet per minute (cfm). Most air impact wrenches run between 4.5 and 5.0 cfm at 90 psi. In an ideal world, you need a compressor that matches the pounds per square inch and exceeds the cubic feet per minute, so you have airflow to spare.
If the cubic feet per minute of your compressor don't match the tool, you'll drain the air tank and have to wait while it repressurizes. Small pancake compressors often have high pressure (150 psi or more) but only 2.5 to 3.0 cfm. Using one of these would get frustrating because with insufficient airflow, the tool simply stops working. You then must wait until the volume in the tank builds up, and pancake compressors often don't have very big tanks anyway.
If you don't already have a compressor, a model of sufficient capacity will probably cost at least $300, but if you compare the price of a high-end electric or cordless tool, you might save that much. What's more, you then have a compressor to run other air tools, such as a grinder or airbrush, so you might save even more.
A note about lug nuts
An air impact wrench is great for taking off lug nuts – after all, it's what the pros do. However, you need to be very careful if you're using one to put them back on again. It's easy to overtighten them, and you can strip the threads or damage the studs.
Experts and auto manufacturers recommend using a torque wrench to retighten lug nuts. It's a different tool that can be set to the precise torque required to do the job properly, so there's no chance of causing problems.
Inexpensive: The cheapest air impact wrenches we looked at cost as little as $40 and come with a set of sockets, too. These are perfectly good tools but often have just a single setting and relatively low torque. Low-cost tools are often noisier, too.
Mid-range: Most home mechanics will probably find what they want in the $100 to $150 range. Tools at this price are generally well made and durable and offer torque of around 600 ft-lbs.
Expensive: Spend around $250 and you're buying professional-quality tools delivering 900 ft-lbs. of torque or more. These are extremely tough tools that will deliver a lifetime of excellent performance.
Premium: Specialist air impact wrenches can cost a lot more – up to $1,500 – but unless you're running your own NASCAR team, you probably don't need to consider these.
If you're looking for a budget air impact wrench for occasional use, the Neiko 30128A is definitely worth a look. With 600 ft-lbs. of torque, it's surprisingly powerful for an entry-level impact wrench and has good ergonomics, too. The Astro 1822 1/2" Nano has been designed to overcome the challenge of getting an impact wrench into tight spaces: this compact tool is just 3 7/8 inches from front to back. Despite its diminutive dimensions, it still produces 450 ft-lbs. of torque, and with three forward and three reverse settings, it's also versatile. The AirCat 1150 Killer Torque air impact wrench lives up to its name, delivering a maximum 900 ft-lbs. of loosening power for a surprisingly reasonable price. And at 86 decibels, it's not particularly noisy.
Q. What's the difference between an air impact wrench and an impact driver?
A. An impact driver is used for screws or similar small fixings. It's most often employed where the number or length of the screws is too much for an ordinary drill or driver to cope with. An impact wrench is an extremely powerful tool for untightening or tightening large nuts and bolts. Most people will have come across one at a garage or tire dealer where impact wrenches are used on lug nuts, though these tools are also used in a wide variety of engineering situations.
Q. Is an air impact wrench better than a cordless model?
A. In a commercial environment (and with race teams at the track), the air impact wrench is still preferred because of the consistent power delivery. There are no concerns about a battery running flat when you need it most. For hobbyists or home mechanics, it's very much a matter of personal choice. Cordless impact wrenches don't need a compressor and hose, so they're more portable, and it may not matter if you have to wait a couple hours for the tool to charge. However, good cordless wrenches can be twice the price (or more) of air tools.
Q. Can I use ordinary sockets with an air impact wrench?
A. They might fit, but most standard sockets don't have the material strength to cope with the forces generated. The rapid impact coupled with the torque can cause them to crack or even shatter, which is very dangerous. It's recommended that you buy specific impact sockets. If the drive is the same size, these can be used with your existing ratchets.