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If you've ever exhausted yourself bouncing up and down on a tire iron, you'll appreciate the power and simplicity of an impact wrench. Instead of enduring a lot of sweat and skinned knuckles, you simply squeeze a trigger, and your lug nuts are removed in seconds.
Until fairly recently, an impact wrench wasn't an option for most homeowners. You might have seen impact wrenches at the garage when you were waiting around for a new set of tires, but the air compressor needed to run them simply wouldn't be found in many DIY toolboxes.
Now you can buy a cordless impact wrench. For the handy DIYer, it’s hard to say no to all that power in one convenient, easily portable package. But which one?
There are dozens of impact wrenches available, and to choose one, you must wade through a host of specifications and options.
Finding answers that help you make good buying decisions is why BestReviews was created!
We test products in our labs, interview experts, and gather impressions from existing product owners. And we never accept free products as an incentive toward a good review. Our goal is to present readers with product information that is completely unbiased.
The impact wrenches in the matrix above are those that met the rigorous standards we set.
For a detailed look at what makes a good impact wrench, we've put together the following shopping guide.
If you're using air tools, check your hoses and connectors regularly. If there's any sign of damage, replace them immediately. A high-pressure failure can be very dangerous.
An impact wrench performs quite a basic job: it loosens and fastens nuts, bolts, and similar fixings. In workshops, factories, building sites, and homes, an impact wrench is an invaluable tool.
Two elements combine to make an impact wrench effective: torque and hammer action. The impact wrench generates tremendous torque to twist the nut – much more than you could create manually. Then, hammer action is added; the impact wrench literally hammers the nut loose while it's being twisted.
Granted, you may not need to use an impact wrench every day. But when you do come across a stubborn nut or bolt, there is no other device that compares with an impact wrench. It's equally fast and powerful when fastening, too.
Product in Depth
Product in Depth
Milwaukee Electric Tool M18 1/2-Inch
The Milwaukee's M18’s dependable motor is the widely used 18-volt, 4Ah version. Because it's brushless, there are no problems with power drain or overheating. Importantly, it delivers impressive torque: 700 ft. lbs. in normal use and up to 1,100 ft. lbs. for cracking stubborn nuts. Its service life is excellent. What’s more, the Milwaukee manages to deliver top performance in a comparatively compact and ergonomic package. At the same time, the manufacturer acknowledges the kind of punishment impact wrenches generally take by encasing the mechanism in a protective metal shroud.
Air-powered impact wrenches, also called pneumatic impact wrenches, often cost less than other types, and they are normally lighter and simpler. This is because there is no complicated motor in the tool itself; an air-powered impact wrench gets its power from an air compressor.
The downside to air-powered impact wrenches is the fact that an air compressor with sufficient power is expensive. It requires regular maintenance, and the tool needs to be attached to it via a high-pressure air hose. The compressor is almost always in a fixed position. The hoses are quite stiff, so they make movement awkward. Also, because pressure drops over distance, hoses can be quite short.
Air-powered impact wrenches are rather plain tools. Because the power comes from a compressor, there are no electrics in the hand-unit. However, many air compressors do have some kind of power regulator on the gun.
Air-powered impact wrenches can cost as little as $25 to $30. But as with all cheap impact wrenches, we advise caution. The stresses endured by an impact wrench are immense, and we have serious doubts about the durability of most low-cost impact wrenches.
Corded impact wrenches are widely available. Though not as powerful as high-end air tools, they're still strong enough for most DIY purposes.
In general, corded impact wrenches are lighter than cordless impact wrenches because they aren’t weighed down by a battery pack. Of course, these wrenches must be plugged into an electrical outlet, which restricts range. An extension cord affords greater freedom, but the cord could tangle, and the trip hazard is a frustrating nuisance.
Corded impact wrenches are low on extra features, but because they're aimed more at the DIYer, they usually have pretty good ergonomics. They're generally comfortable to hold, and some corded impact wrenches have handles specifically designed to reduce vibration.
Err on the side of caution when fastening with an impact wrench. They produce a lot of torque very quickly, making it easy to do serious damage if you're not careful.
A cordless impact wrench would seem the ideal solution. Like corded models, they don't have quite the performance of pro air tools, but they come close. What’s more, you enjoy complete freedom of movement with a cordless impact wrench.
The drawback, as with all cordless tools, is battery life. To some extent, it's less important because an impact wrench uses short bursts of energy rather than running constantly. There is still a notable power drain, though. If this is a concern for you but you want a cordless impact wrench, consider purchasing a kit with an additional battery.
Some cordless impact wrenches have a useful LED worklight. Any additional effort on the part of the manufacturer usually goes toward increasing battery life. Twin or variable speed can help. Some batteries have charge level indicators, which is convenient. If you opt for a cordless impact wrench, a battery charger is a must. A spare battery is a nice bonus, as is a bag or hard-shell case.
An air-driven impact wrench is an extremely powerful tool, but due to the nature of the tool’s price and the air compressor required to run it, it is best reserved for static, professional use.
If you choose a cordless impact wrench – the most popular choice among home users – the battery you use can make a significant difference in the wrench’s performance.
There are two important figures to know when it comes to batteries: volts (V) and amp hours (Ah). Volts tell you the amount of out-and-out power available. Amp hours tell you approximately how long that power can be maintained. For example, a 1Ah battery can supply a one-amp current for one hour, a two-amp current for half an hour, and so on. A 2Ah battery will run at the same level for twice as long.
To apply the actual math to an individual tool is too complicated to go into here. Put simply, a 20V, 5Ah battery will deliver performance for considerably longer than a 20V, 2Ah battery.
Beware the price of a “bare tool.” At first glance, a bare tool seems like a bargain – until you realize that the battery is not included. Make sure you’re aware of the full price before buying.
Hydraulic impact wrenches are rare. They produce considerably more torque than air tools and are only found in heavy industrial situations.
With all other types of impact wrenches, the tool is taken to the job. But due to the size of a hydraulic impact wrench, the job is typically taken to the tool.
Product in Depth
Product in Depth
Ingersoll Rand Hi-Torque Impact One
Quality on a Budget
The Ingersoll Rand does just about everything most budget impact wrenches do, and then some. The 20-volt motor is among the most powerful available. Its torque figures of 1,100 ft. lbs. or 780 ft. lbs. are outstanding. It includes the friction ring socket attachment that professionals prefer, and it's built like a tank – though it's not bigger or heavier than much of the competition.
While the weight of your impact wrench may not initially seem of much importance, if you've got to lug one around all day, it can make a difference.
Air-powered impact wrenches are the lightweights, weighing from 5 to 8 pounds.
Corded impact wrenches weigh approximately 9 to 11 pounds.
Cordless impact wrenches are the heavyweights – largely because of the battery pack – weighing from 10 to 15 pounds.
Impact wrenches are loud. Always wear ear protection when using an impact wrench.
The standard "pistol grip" impact wrench looks much like your favorite electric drill/driver.
There are also "inline" impact wrenches. These tools look a lot like an electric screwdriver. The body is slim enough to hold comfortably. The anvil (the part where you attach your socket) is at the end and can be in line with the body or turned at right angles.
Though many sizes are available, inline impact wrenches are generally used for smaller nuts and bolts and in places where space is restricted.
Always hold pistol-type impact wrenches with both hands. One hand should be on the handle; the other hand should be around the top. The torque could cause serious wrist injury if you don’t grip the wrench firmly.
Impact wrenches come with a variety of anvil sizes. The anvil is the place where you attach the socket, and its size governs the size of socket you can attach.
The smallest anvils (1/4”) are found on inline and pistol grip tools.
The remainder of commonly available sizes are usually found on pistol grip models. These sizes include 3/8", 1/2", and 3/4".
Larger anvils of one or two inches do exist, but unless you're putting together an oil rig or cargo ship, you're unlikely to come across them.
All impact wrenches come with two kinds of anvil: detent pin or friction ring (also called hog ring). Both are a quick-change mechanism for sockets. Detent pins tend to be a little stiffer, so while potentially a firmer grip on your socket, they're also slower to change. People who need to change sockets often usually favor a friction ring anvil.
Anvil reducers are available, so if you buy a 1/2" model but need to use a 1/4" socket, you can get a converter for just a few dollars. Extension bars are also available to reach into awkward places.
There are three figures to look at when assessing impact wrench performance:
Revolutions per minute, or RPM
Impacts per minute, or IPM
Torque, also known as “twisting force,” is the star feature on any impact wrench. In general, you could say the more torque, the better – with a couple of provisos.
With air-powered impact wrenches, the air pressure has a major effect on the torque generated.
With corded and cordless impact wrenches, torque comes down to the electric motor.
High levels of torque can be produced by all these tools, but it is also vital that the torque is controllable.
Often, cordless impact wrenches will quote two figures: a fastening torque and an unfastening (or “nut-busting”) torque. The first figure is lower. Over-tightening can be a problem, stripping threads and even breaking heads off fixings, so tightening torque is reduced.
Unfastening torque needs to be as high as possible. In this mode, cordless impact wrenches run at their absolute maximum.
Always make sure the socket is a proper fit, or you risk rounding the head of your fixture and making it unusable.
The RPM of an impact wrench is not a major factor when unfastening, because the main job is “cracking” the fixture. When fastening, a higher RPM means the job will be done quicker. That said, the difference between models is usually very slight.
IPM refers to the frequency of the hammer action. Higher numbers are better. This figure can be useful when comparing similar impact wrenches to one another, but IPM is generally thought not to be of great significance. In fact, several major brands don't quote IPM at all.
Impact wrenches need little maintenance, and it's easy to overlook it. Don't. Always follow the manufacturer’s instructions. It takes minutes but can add years to the life of the tool.
Corded impact wrenches are the best option for those on a budget. A good corded impact wrench may cost as little as $70. The best in this bracket run only to about $150.
Small, inline impact wrenches from a reputable brand cost around $100. Pistol air tools range between $100 and $200; extremely heavy-duty models may cost a bit more.
Cordless impact wrenches sit at the top the pile in terms of price. Expect to pay $250 for a good cordless impact wrench and $400+ for the best. This is a sizable investment, but the combination of power, convenience, and durability is hard to match.
Q. I get confused about the differences between an impact driver, a torque wrench, and an impact wrench. Can you clarify the purpose of each?
A. An impact driver is like a very powerful electric screwdriver. You may have experienced times when a cordless drill/driver just wasn’t up to the job. For example, putting a four-inch screw through an oak beam is too much for a cordless drill. Instead, you’d need an impact driver.
A torque wrench is used on things like cylinder heads. That makes it sound like a powerful tool, but a torque wrench is actually capable of very fine adjustments. It's used for fastening when a precise amount of torque is important. It has a mechanism that prevents it from exceeding the pre-set amount. A torque wrench is never used for undoing things.
And, as mentioned above, an impact wrench is designed to loosen and fastens nuts, bolts, and similar fixings.
Q. Which battery type is best for a cordless impact wrench, NiCd or Li-ion?
A. Nickel-cadmium (NiCd) batteries are an established technology and also relatively cheap. Unfortunately, as power runs down, a NiCd’s performance drops off sharply. Lithium-ion batteries (Li-ion) are smaller, hold their charge longer, and deliver power more consistently. Though they are more expensive, most brands favor them.
Q. Some electric impact wrenches have brush motors; others have brushless motors. Is one better than the other?
A. This question has some parallels with the above question about batteries. You have a long-established technology, the brush motor, and a more recent development, the brushless motor.
Brush motors are cheaper, and though noisy, they are perfectly reliable. But brushless motors make much more efficient use of the power available, have fewer moving parts, don't get so hot, and require no maintenance. Bottom line: unless you're on a restricted budget, a brushless motor is the better choice.
At BestReviews, we purchase every product we review with our own funds. We never accept anything from product manufacturers. Our goal is to be 100% objective in our analysis, and we do not want to run the risk of being swayed by products provided at no cost.