Impact Wrench Buying Guide

Last updated: Tuesday, July 25, 2017

Impact Wrench Buying Guide

If you’ve ever been unfortunate enough to have been laid on your back, straining until your veins are ready to pop due to a corrode or stubborn fitting or nut, you’ll know what value an impact wrench offers. To many, they seem overkill – that is until you’ve suffered this scenario yourself, absolutely needing to have one to finish a job or project.

Just a decade ago, all good impact wrenches were air-powered, requiring a bulking compressor to deliver performance that was up to the job of tightening and loosening nuts and bolts. Today, this is no longer the case, with there now being a wide range of electricity – both mains-powered and cordless – impact wrenches on the market, thanks to advances in technology over recent years.

Cordless Impact Wrenches

Out of the 3 different types of impact wrenches – these being air-powered, mains powered and battery-powered cordless impact wrenches – the latter of which offers a number of significant benefits over the others. These benefits, some of which are obvious at first glance – such as their portability, thanks to being powered by rechargeable battery packs, which adds considerably to the wide range of application of cordless impact wrenches. There are some drawbacks, notably being their heavy-weight, however, these far outweigh the benefits for these impact wrenches, which offer a lot more when it comes to value than other types.

We’ve taken a close look at some of the best cordless impact wrenches on the market, reviewing and ranking them by their build quality, their range of features and the value for money that they offer, to help you make an informed decision on which impact wrench is right for you.

Dewalt DCF899P2-GB 18V (£349.99)

The Dewalt DCF899P2-GB 18V is a high-torque, brushless impact wrench that delivers up to 50Nm of torque and 2,400 impacts per minute. It comes equipped with 3 different torque settings and a high-intensity LED. This impact wrench features a powerful, fan-cooled electric motor which is perfectly suited to heavy-duty fastening applications and is powered by a 5.0Ah Li-ion rechargeable battery pack. This cordless impact wrench from Dewalt offers a lot of value over other, similarly priced tools – which is exactly why we’ve selected it as the best impact wrench on our list.

Product features

  • Bright white LED with delay feature for improved visibility and flashlight functionality
  • Comfortable rubber XR grip and switch for greater application comfort and maximum control
  • 1/2″ (13 mm) square drive with detent pin allows for more efficient torque delivery and excellent socket retention
  • 3 Speed and torque settings gives you the control to best suit your application
  • Up to 1625Nm of “breakaway” torque ensures removal of the tightest bolts

Milwaukee HD18HIWF402 18V (£289.99)

The Milwauke HD18 HIWF-402 is an 18V, cordless impact wrench that offers up to 610 Nm of torque, making it well suited to even the toughest applications. It features a friction ring, allowing for quick and easy socket release, and is powered by a 4-pole frameless motor. Designed with durability in-mind, the Milwauke HD18 HIWI-402 is ideal for those working with heavy applications, including car maintenance, industrial construction, steel fabrication and mechanical fastening. It is also equipped with a fuel gauge display, which indicates how much power is left in its rechargeable battery pack and boasts an ergonomic, light-weight design compared to other impact wrenches in its class.

Product features

  • Friction ring for quick and easy socket release
  • 4-pole frameless motor
  • Redlink overload protection electronics in tool and battery pack deliver best in class system durability
  • Light weight and ergonomically designed
  • Fuel gauge displays remaining battery charge state

Makita DTW251RMJ 18V (£319.99)

The Makita DTW251RMJ is an 18V impact wrench that offers up to 230Nm of torque and 3,200 impacts per minute, making it ideal for use in steel erection, car maintenance, and steel fabrication. With its light weight and compact size, the Makita DTW251RMJ provides more maneuverability and control than other impact wrenches in its price range, making it much easier to use in those harder to reach places. This tool is powered by a 4-pole motor and uses a LXT Lithium Ion 4Ah rechargeable battery pack, it also comes equipped with an LED light with after glow function and phosphorescent, high-visibility bumper.

Product features

  • 18 V LXT Lithium Ion Impact Wrench
  • High operational efficiency with high torque
  • Ideal for steel fabrication, steel erection or for automotive work
  • Able to deliver up to 3200 blows per minute this little machine will make your life much easier
  • Maximum fastening torque of 230Nm (170ft.lbs)

What is an Impact Wrench?

The primary purpose of an impact wrench is to assist with the loosening and tightening of nuts and bolts, by reducing the amount of effort needed to be exerted by the user to do so, making the process more efficient. There are a number of different types of impact wrench available, however, these fundamentally work in the same way. Impact wrenches essentially work by applying a rotational force, referred to as torque, in short bursts, known as impacts, and are driven by a motor that can be powered by air, mains electricity or in the case of cordless impact wrenches, by a rechargeable battery pack.

As this force is applied in short bursts, the user can apply far greater torque to the fixing than they would be able to by hand, using a regular wrench. This ability – to greatly reduce the level of effort required by the user – an impact wrench can help to reduce fatigue and any risk of injury or strain. It also results in reducing the time required to complete a task, allowing the user to finish their job or project far quicker than they otherwise would be able to.

The pistol grip is the most popular impact wrench style – featuring an “L” shape that makes the tool both easier to control and hold that other types. Another benefit of the pistol grip design is that it has a smaller profile, making it easier to access tight and otherwise hard to reach spaces. This shape is available as an option for all types of impact wrench – being available with both electric and air-powered tools.

After pistol grip impact wrenches, the next most popular design is in-line – a design where the tool’s body is straight with the grip, with the anvil sticking out of the end in order to mount your socket. The position of your hands when using this shape is similar to that of a screw driver, making them less easy to control thank pistol grip impact wrenches, which is why you’ll find that these tools are typically used in lower torque applications.

Impact wrenches are available in all standard drive sizes, from 4.5 mm to 13 mm, as well as larger drive sizes that are typically used on building construction sites. For professional and personal applications, the most common drive sizes of impact wrenches are 13 mm and 10 mm.

How an Impact Wrench Works

An impact wrench is equipped with a motor – either electric of air-powered – that is designed to apply sudden, intense twisting motion in short bursts to a difficult lug nut, working to either loosen or tighten it. Indeed, the tool is ideal for both assembly and disassembly projects.

In addition to the twisting force exerted on a nut by an impact wrench, it also applies pressure that works to push the fastener forward. This action allows an impact wrench to work far more effectively on a fastener than you could ever hope to if working it by hand.

As already mentioned, impact wrenches are powered one of two ways – either by air, also known as a pneumatic impact wrench, or by electricity. Whilst both types of impact wrench will be up to the job for most projects, pneumatic impact wrenches are considered more professional-grade, as they typically deliver more torque than their electric counterparts. The biggest drawback of these impact wrenches is the need for an air compressor, something that makes an electric impact wrench far more suitable for taking with you on the road.

Impact Wrench vs. Impact Driver

When searching for an impact wrench you’ve no doubt come across impact drivers and may be curious to know how these tools differ from impact wrenches. While at first glance there is some overlap between these tools, in terms of functionality, they aren’t one in the same, nor are they interchangeable.

Each of these tools provides a lot in the way of torque, using a rotary hammering action that is designed to deliver sudden, rotational force. This force is highly effective when it comes to providing more force than a conventional cordless drill offers. Impact drivers differ from wrenches as they provide an additional, downward force – something which works to loosen stuck bolts and screws without stripping them.

Another difference between an impact wrench and an impact driver is that they’re usually equipped with a female, quick-release hex chuck – whereas most wrenches feature a standard 13mm or 10mm square drive.

When and Why to use an Impact Wrench

Impact wrenches are designed with one primary use in mind – installing and removing nuts and bolts. Whether you’re using an impact wrench to rotate tires, remove lug nuts, subframe bolts or rod-bearing caps, an impact wrench is designed to make light work of these, making it more efficient and faster to complete such tasks.

It’s worth noting that it is possible to tighten fasteners with an impact wrench as well, however, it’s recommended that you don’t torque bolts all the way with an impact wrench to avoid damaging them.  The best way to avoid such damage is to turn the screw most of the way down with an impact wrench, after which tightening of a bolt should be finished by hand.

When it comes to the question of why you’d use an impact wrench, the answer is simple – the primary advantage they offer is to allow you to remove a fastener quickly, without needing to exert yourself doing so by hand. This makes completing any task that requires the removal of multiple bolts – such as in car maintenance – far quicker with an impact wrench, then without one. An impact wrench is also an essential bit of kit when dealing with those nuts that just won’t budge, a situation where you’re going to be incredibly thankful that you have one.

How Not to Use an Impact Wrench

Perhaps the biggest risk when using an impact wrench is the over-tightening a fastener – something that can often result in stripped threads or weakened bolting joints, which could subsequently fail without warning. It is also possible, if too much torque is applied, to twist the head off a bolt which will result in you needing to waste significant time and energy to drill the bolt out. If you’re reading this and have never had to drill out a bolt, you’re one of the lucky ones, as doing so can be a huge annoyance. To avoid over-tightening, the best method is to stop short and finish torquing by hand.

Another common problem people run in to when using an impact wrench is that they try to use it to begin threading a bolt. If you intend to drive a bolt in using an impact wrench, it’s advisable to start it by hand first. By doing do, you’ll ensure that you avoid cross threading the bolt.

When using an impact wrench, it’s important that you use a socket that is designed for it – not a standard socket, as these tend to be made with thinner walls that are susceptible to cracking. Standard sockets strip out and wear very quickly and tend to break when used with an impact wrench, send pieces flying everywhere. Make sure that your pick up a set of sockets designed for use with an impact wrench before you start.

Lastly, wear eye protection when using an impact wrench. It’s always a good idea to wear a pair of safety glasses whenever you’re placing force on metal components in case something chips off. Not doing so could fast turn a minor annoyance into a serious emergency that requires a trip to accident and emergency.

Different Types of Impact Wrench

Impact wrenches fall into one of three categories – air-powered impact wrenches, battery-powered impact wrenches, commonly referred to as cordless, and electric impact wrenches. The difference between these types is how they are powered, with battery-powered and electric impact wrenches being used with standard wall sockets, whilst air-powered impact wrenches require a separate air compressor.

For home-use, the most common are battery-powered impact wrenches due primarily for the level of convenience that they offer. Other types – particularly air-powered impact wrenches – are the least common, due to their requiring an air compressor and hose, which most people don’t have around the house.

Which Type of Impact Wrench is Right for Me?

Each of the three types of impact wrench – air, electric and cordless – have their own advantages and disadvantages over one another.  First generation impact wrenches were all air-powered and were used only by professionals and race mechanics as a means of quickly removing and refitting wheel nuts. This remains the case today, with air-powered impact wrenches remaining the tool of choice for those who require them in a professional environment. This type of impact wrench is also not very well suited to infrequent or home use – as to operate, they must be attached to a compressed air supply line, which can make them difficult to use in a restricted workspace.

Standard electric impact wrenches – those that have a cord – can also be impressively fast and powerful, depending on the make and model you decide on, but are far less robust than air-powered ones. Like pneumatic impact wrenches, one of the most notable disadvantages is the lack of portability, due to the tool being powered directly from a power outlet, as opposed to by a battery, as is the case with cordless impact wrenches. This type of impact wrench does, however, tend to be far less expensive than both air and cordless wrenches, making them particularly attractive to DIY enthusiasts and hobbyists who intend to use them at home.

The most sought after of the three types is the cordless impact wrench. In recent years cordless power tools have improved dramatically, thanks to improving technology, so much so, in fact, that high-end cordless impact wrenches offer a level of performance that is approaching that of their air-powered counterparts. Being cordless, these impact wrenches are completely portable, making them easy to move around a workspace and when trying to reach harder to access areas. There are however some drawbacks to this, notably their weight due in part to their heavy battery packs.

Air, or pneumatic impact wrenches, remain the most widely used by professional mechanics, however, as technology improves, the cordless impact wrench are increasingly becoming the tool of choice, and will eventually dominate the impact wrench market.

Things to Consider When Buying an Impact Wrench

There are many factors to consider when buying a new impact wrench, many of which will determine whether or not the tool you decide to buy is suited to your intended use – both in terms of the types of project you will use it on, as well as how often you will be using it. If you’re the sort of person who uses an impact wrench occasionally at home, then your requirements are going to vastly differ from someone who requires an impact wrench every day of the week as part of their job. Below you’ll find a list of some of the more significant factors to consider before deciding which impact wrench is right for you and your need.

IPM, Power and Torque

Perhaps the most important factors to consider is the torque and IPM – impacts per minute – that a particular impact wrench offers, as these will have the most significant impact on the effectiveness of an impact wrench. It’s also worth considering how you want your impact wrench to be powered, whether by air, mains electricity or battery, as in the case of a cordless impact wrench.

Build, Design and Weight

An impact wrench is unlikely to be the lightest tool in your box – especially if you’ve opted on a cordless impact wrench – and as such, it’s important to find one that offers a good level of comfort and ergonomic design to counter this. As these tools take a bit of a beating during regular use, it’s advisable to choose one that benefits from a high level of build-quality, as this is vital to the durability of an impact wrench.

Features and Warranty

There are a wide range of features available – from multiple speeds, to in built lights that help to illuminate dark corners – each impact wrench on the market will have vastly different features, some of which may be better suited to your intended use. An impact wrench works extremely hard to deliver the torque needed to be effective – considering this, it’s important to get one with a good and lengthy warranty, especially if you’re going to use it frequently.


The best impact wrenches don’t come cheap, but you get what you pay for. If you’re going to use your impact wrench infrequently, this might not be a problem, but if you use one professionally, going for a more premium, high-end model is going to pay off in the long-run.

When weighing up the significance of each of the factors given above it’s important to remember that the significance of these very much depends on your intended use for an impact wrench, with different applications having different levels of priority for each factor. Provided you keep this in mind when deciding on which impact wrench to buy, you show have no problem choosing one that’s perfect for the job or project you require one for.