Power tools are often multi-functional in use but one power tool that is quite specialised in its application is the impact wrench which is focused on the undoing of difficult-to-remove nuts and bolts. Although historically the air-powered impact wrench has been the dominant form in use, mostly in the hands of professionals, in more recent times, the electric version of the impact wrench has started to find its way into the tooling arsenal of the DIYer. This is the type of impact wrench that we focus on here.
In this review of electric impact wrenches, we first look at how this power tool is used and what makes it different from other similar tools like the impact driver. Then, since you probably stumbled upon this review as part of research into buying one, we examine the different technical specifications that are present in today’s crop of electric impact wrenches with a view to establishing what to look for when purchasing one. Finally, once we have figured out what the best impact wrench is likely to look like, we then delve into actual popular electric impact wrenches that are for sale in the UK today.
The Impact Wrench for the DIYer
The impact wrench is mostly known for its use in the automotive industry, but it also plays key roles in the maintenance of other machinery and infrastructure or construction projects. In the case of the DIYer, he or she will likely buy an impact wrench also to make the changing of wheels on a car or other vehicle a breeze, but the impact wrench may also see use in the assembling or disassembling of other machinery in or around the home or in a home construction project. Impact wrenches are sometimes the only tool that will release a stubborn or seized fastener, which it achieves through the creation of a high-torque hammering action at the interface with the fastener. Since the high torque is only briefly applied with each blow of the ‘hammer’, the operator actually feels very little reactionary torque in the opposite direction making the impact wrench easy to use by anyone. In addition, the impact wrench requires a minimum resistive torque in order for the high torque hammering action to get going meaning that the tool can also be used to undo or fasten nuts and bolts that are not necessarily stuck.
Impact wrenches come in a variety of sizes with one of the most common sizes purchased by the DIYer being the 1/2” machine (the 1/2” referring to the size of the drive shank or anvil). As alluded to earlier, impact wrenches also come in different power system formats, including those that are powered by air, mains electricity or batteries. Air-powered impact wrenches are the most common form amongst professionals who usually have ready access to the more powerful air compressors needed to operate them, but even some DIYers also favour the compressed air-powered impact wrench. In more recent times however, the electric impact wrench has started to make more headway into the consumer market as it is simpler to use, more portable, and doesn’t need a separate air compressor to power it. Electric impact wrenches were originally mains electricity-powered, but with recent advances in battery technology, cordless battery-powered machines have started to predominate amongst consumers. In general, air-powered impact wrenches are cheaper, lighter and have higher power-to-weight ratios than their electric counterparts, while amongst electric impact wrenches, mains-powered corded machines usually have more power output than their cordless battery-powered siblings. However, in terms of convenience of use, the opposite is usually true with cordless electric impact wrenches often being ready to use with the minimum of setup.
Impact Wrench vs Impact Driver
The impact wrench is a similar but distinct power tool from the impact driver which is used to remove stubborn screws instead of nuts and bolts. The main differences between the two impact tools are the level of torque each can output and the type of driving shank fitted onto the machines. Impact wrenches usually can output higher maximum torque than impact drivers and they have square male anvils that insert into bespoke socket sets. In contrast, the impact driver, has a female hexagonal bit holder, usually 1/4” in size, that is essentially the same as those found on other types of electric screwdrivers (and some manual ones too).
Chrome Socket Sets: can they be used on an Impact Wrench?
The simple answer to this is no, impact wrenches need their own set of special impact-resistant sockets. That’s because the use of regular sockets that are used on regular socket wrenches are liable to being damaged by the high-impact high torque action of the impact wrench since the metal they are made from tends to be more brittle. Specialised impact wrench socket sets are needed for use with an impact wrench, and they are usually black in colour as opposed to the more common chrome sockets that regular socket wrench devices use.
Can an Impact Wrench be used to fasten Nuts and Bolts?
Another common question with impact wrenches is whether they can be used for screwing on fasteners. Although the impact wrench can screw on fixings successfully, using an impact wrench for this sort of work risks over-tightening the fastener, stripping it or even breaking it if one is not careful, due to the relative uncontrolled application of the high amounts of torque from the impact wrench. This is even more important to consider for fasteners that need to be set to specific torque levels like those on vehicle wheels where a torque wrench is required.
What to look for in an Electric Impact Wrench
Corded vs Cordless
As alluded to above, electric impact wrenches can be either mains-powered (corded) or battery-powered (cordless) and this represents one of the first major decisions one must make when looking to buy one for the home workshop. Some of the decision will be based on personal preference, but one should also consider where the tool is going to be used especially with regards to access to mains power. In general, corded impact wrenches are the domain of the less reputable brands of power tool retailer but they also tend to provide more power at a lower price point. More reputable name-brand power tool manufacturers, better known for selling higher quality power tools, tend to focus almost exclusively on the cordless battery-run impact wrenches.
For mains-powered electric impact wrenches, the power input level is measured in Watts (W). In general, higher wattage means a greater maximum torque the machine can produce, so for corded impact wrenches one wants to lean towards the highest powered machine that is affordable. In the case of battery-operated impact wrenches, power is delineated in voltage (V) and generally speaking, the higher the voltage, the higher the power the tool can output. Battery-operated impact wrenches come in a small set of discrete voltages usually as 12V, 18V, 24V or sometimes 36V which is usually dependent on the size of the power tool. In the case of the 1/2” electric impact wrench common with DIYers, batteries are typically the 18V (or sometimes 20V) variety.
Somewhat correlated with the power at which the electric impact wrench operates, one of the key specifications to look at when choosing an electric impact wrench is the maximum torque that it can deliver (sometimes referred to as the maximum fastening torque). This is defined by the highest peak torque delivered by the impact wrench when locked into a perfectly solid object. Obviously choosing an electric impact wrench with the highest maximum torque that is within one’s budget should be the key driver here. However, another type of torque metric called the “nut-busting” maximum torque is also sometimes provided by manufacturers which can lead to some confusion. As its name suggests nut-busting torque is defined by as the ability of the impact wrench to loosen a nut with the specified amount of torque in some specified time period. Since the ‘specified time period’ of the nut-busting torque metric just introduces another variable which may be different from manufacturer to manufacturer, the nut-busting specification may not be as useful when comparing between impact wrenches, with the earlier described maximum torque specification being the better metric for comparisons.
No-Load Speed (rpm)
The no-load speed refers to the number of revolutions per minute (rpm) at which the motor spindle in the impact wrench turns. In simple terms, the faster the spindle turns, the higher the force at which the ‘hammer’ will strike a stuck fastener. Therefore, by controlling the no-load speed, impact wrenches can have variable maximal torques. In practice, this comes in the form of different gear settings on the impact wrench, which can provide a small set of discrete maximal torques from the machine.
The impacts-per-minute of an impact wrench refers to the rate at which the hammering action of the machine is delivered. Intuitively, one can deduce that the higher the rate, the more often the peak torque is applied to the nut being loosened and should result in a faster end result. In reality, however, the rates of any impact wrench are all sufficiently high that differences in the speed of the ‘nut-busting’ action will likely be minimal. So unless the impact wrench is needed for some highly competitive event, such as NASCAR or Formula One racing, the impacts-per-minute metric will be mostly irrelevant to the regular user.
Impact wrenches tend to be relatively heavy power tools for their overall size, with the additional working parts in electric versions making them even heavier. As a consequence, weight is an important metric to take into account when purchasing an impact wrench especially if the tool is to be used over long stretches of time. In the case of some cordless battery-operated impact wrenches, particularly from the more established power tool companies, a range of different capacity batteries are often compatible with the impact wrench. Consequently, the overall weight of the battery-powered tool can vary depending on the size of the battery installed.
Impact wrenches are inherently noisy machines, especially compared to other power tools, with ratings generally above the 100 dB level. This means that ear protection should be used especially when using the impact wrench over long periods of time or on a regular basis.
Impact wrenches are generally quite bulky tools that can be vulnerable to damage if not cared for. One accessory that is always highly recommended for such tools is a carry case to protect it during storage and transportation. Carry cases for the impact wrench usually come in one of two forms, a soft material bag-type case or a hard plastic case, with the latter type generally being the more favoured for its greater robustness.
Popular 1/2-inch Electric Impact Wrenches in the UK-- Information not currently available
* Weight includes battery pack (if battery-powered)
** The use of different battery pack sizes changes the overall weight of the impact wrench