5 Worst Impact Wrench Mistakes

1. Over tightening fixings

This is probably the most common mistake people make when using an impact wrench for the first time. In an effort to ensure that the nut or bolt is adequately tightened, they stretch or strip the threads. Strictly speaking, an impact wrench is designed to loosen fixings rather than tighten them. It can also be handy for the fitting & removal of nuts or bolts to save time but, as you will discover, this can lead to another mistake.

Even if there is no damage to the threads, excessive tightening of nuts and bolts can cause problems.

Most of us will have experienced the scenario of struggling to remove a wheel nut (lug nut) to change a tyre that’s been fitted by a mechanic with an impact wrench. If tightened to the manufacturers specifications, the nuts can usually be removed by hand, using the wrench provided.

To stop nuts being over tightened, some of the more expensive units now have built-in torque limiting devices. This method is not suitable for tightening to a precise torque setting but it's ok for tightening fixings with a broad tolerance on the torque setting, General fixtures, like lightweight paneling for example, can be tightened with a torque-limited wrench because they are not safety critical. On the other hand, a critical component like an engine bolt or chassis fixing must be tightened to the correct torque setting by hand, using a torque wrench.

Tightening a nut or bolt beyond the specified torque value could result in stretching, which could lead to the fixing losing tension or failing. Stripping the thread, however, is a more common event and one that most of us will have had to deal with at some time. Repairing a stripped thread can be a costly task, in terms of both time and money. It is important to note that most manufacturers quote torque figures for clean, dry threads. Always check with an experienced professional if your threads are not clean and dry and you are tightening a safety critical fixing.

In conclusion, the best course of action is to use an impact wrench for loosening and removing/refitting nuts and bolts, and a torque wrench for tightening them to the manufacturer’s specified torque.

2. Thread damage

Damaging threads is usually caused by cross-threading the nut or bolt prior to tightening it with an impact wrench. The best way to avoid this is to ensure the nut or bolt it correctly threaded by hand before using the impact wrench. Your hands are much more sensitive than a torque-limited impact wrench so use them first. Soft metals, such as brass, are more easily damaged by cross threading than harder metals so this method is particularly useful when working with these materials. If a fixing is too tight to thread by hand it might need modifying or cleaning with an appropriate tool.

A useful tip is to use helicoils in situations where a nut or bolt is regularly fitted and removed from a soft metal or is under high load.

3. Using the wrong sockets and damaging fixings

Many inexperienced people use regular sockets with an impact wrench, which inevitably leads to them slipping. Ordinary sockets are not designed to be used with a cyclic load so tend to wear quickly and become oversized, causing them to slip on the fixing. Impact wrench sockets are heavy duty and grip across the flats (for hex fixings) to prevent them wearing, damaging the fixing and slipping.

4. Buying an impact wrench that is oversized or undersized for the task

Another common mistake is buying the wrong size impact wrench. If the tool is too large, it may be difficult and tiring to use but if it's too small, it might not be up to the task so it can be hard to decide what size to buy. One way to think about it, is to consider what size of hand socket wrench you'd use for the job, as mentioned in my "Beginners Guide to the Impact Wrench". For example, you wouldn’t use a 1-Inch drive hand wrench to release a 3/8-Inch nut, and the same applies to an impact wrench.

Next, consider where you will be using the impact wrench and how long for. For example, for use in tight spaces an air impact wrench is smaller and has a better power-to-weight ratio than an electric one making the more suitable choice. This is why electric or cordless models are usually better for home use because you don't need a compressor and airline, whereas air is preferred by professional garages where they have the equipment on site.

From a more technical perspective, if you know the torque required to release your largest fixing, then you can check this against the torque rating of the impact wrench. As long as it has a rating greater than the required torque, you shouldn’t have any problems. If the fixing has corroded or fretted however, you may need more torque to release it than the value it was tightened to. To overcome this problem, as a general rule, factor in a 20-30% higher torque rating than you originally estimated.

5. Purchasing the wrong model of impact wrench

Similarly to mistake number 4, people often buy the wrong type of impact wrench. Depending on the task, each type has its own positive and negative features. Air tools have the optimum power-to-weight and power-to-volume ratios and so are preferred by race mechanics and garage workers. For occasional home use, electric tools are a good option as they have a good power to weight ratio and are generally less expensive. Cordless tools are the only portable option but tend to be larger, heavier and more expensive than air or electric units. Additional features such as a torque limiter, battery indicator or extended warranty should also be carefully considered to ensure you get the right tool for the job.

To help you avoid these mistakes, our impact wrench reviews are written to guide you through the process from beginning to end. If you are still uncertain which model is best for your application after reading the reviews, ask your question in the comments below the reviews and we will do our best to assist you. Otherwise, please contact us directly and we will try to answer your query to the best of our knowledge.

Guidelines for choosing an Impact Wrench

If you’ve ever experienced trying to loosen a large, fretted or corroded fixing, then you’ll appreciate what I’m about to say. Often working in tight spaces or at awkward angles, nuts and bolts can be extremely difficult and time consuming to fit or remove. People all over the globe face numerous problems when working with nut and bolt fixings, including jobs taking too long, broken tools and injuries to the hands. Despite having access to special tools and equipment and a wealth of experience, even fitters and mechanics frequently struggle with nut and bolts.

How can this problem be solved? The tightening or loosening of a fixing is directly related to how much torque you can apply. Correctly tightening or releasing the fixing can't be achieved without the right input torque. Furthermore, it is very important for busy mechanics, and even people at home, to be able to undo fixings in difficult locations, quickly. Similarly, the time taken up by repetitive jobs, like removing and refitting vehicle wheels, can really add up over the course of a day and eat into your profit margin or your family’s patience.

These problems can be eased with the use of an impact wrench. It is capable of delivering a much larger force than you can apply by hand, without additional leverage, and it greatly speeds up the tightening and loosening of fixings, especially those that are hard to reach. I'm sure many of you will understand what I'm saying and you'll definitely want to read on.

What is an impact wrench and how does it work?

An impact wrench is a power tool which is used by people to assist the removal and refitting of nuts and bolts, as it reduces the time taken and the effort needed to tighten or loosen them. There are a variety of different types on the market but they all work in fundamentally the same way. A short burst, or impact, is applied to the fixing in a radial direction, causing a torque spike. There are 3 different types, which are powered by mains electric, air or battery (cordless).

The user can apply a much greater force to the nut or bolt than if they were using a hand tool, as the torque is applied in short impacts. This greatly reduces the effort required by the user, which results in less fatigue and fewer injuries or strains. Especially in the case of a professional user, the time to complete a job can be reduced greatly, meaning more work can be done in the same time making the business more profitable.

But which type is best for my needs?

The 3 types of impact wrench, battery, electric and air, all have their own advantages compared with the others. Garage and race mechanics have long used air impact wrenches to remove and fit lug nuts or wheel nuts, until recent years when many have changed to cordless. Depending on the model, air tools are powerful, fast and robust making them ideal for use in a professional environment. However, they do require a large volume, high pressure air supply to operate and regular maintenance, which means they aren’t really suitable for infrequent or home use. It can also be difficult to move an air wrench around the workshop because it must be attached to the compressor with an airline at all times.

Although less durable than similar air impact wrenches, electric impact wrenches are also fast and can deliver very high torques. Of course, they cannot operate without a mains electricity supply and so have the same problem as air tools when it comes to moving around your garage. However, they can be less expensive than air or cordless impact wrenches, making them an attractive choice for home use. Cordless, or battery, impact wrenches have recently become much more popular with mechanics and home users alike. The more expensive, higher voltage units deliver performance approaching that of an equivalent air tool but without the additional infrastructure. They are also completely portable and the absence of a cord means they can be moved easily around a workspace and used in hard to access areas. However, one point to consider is the weight of the battery packs, especially with less expensive units, as it can lead to operator fatigue.

At present, air impact wrenches remain the most popular with professional mechanics but, as technology continues to improve, the cordless impact wrench will become increasingly popular, less expensive, and ultimately dominate the market.

Ok, but how do I choose a particular model?

To find the tool that's right for you, browse through our impact wrench reviews and look for the one that has everything you need. Only the best selling units are reviewed to save you having to trawl through hundreds of reviews, which usually leaves people more confused than when they started. To describe the size of nuts and bolts that an impact wrench can be used with, we use terms such as 'large' or 'medium' throughout our reviews. When in doubt, always choose the larger capacity impact wrench but you can use these terms as a rough guide. It’s very difficult to specify the exact size of fitting because it is a function of the torque rather than the size and is greatly affected by the condition of the fixing. For example, a rusted fixing would need much more torque to release it than a new one. Another tip for selecting the right size of impact wrench is to consider what size of sockets you would normally use with a 3/8” or 1/2" drive. Other considerations such as design, comfort and socket retention system are self-explanatory and should become clear from reading the reviews.

An impact wrench is a great investment; it takes the strain out of removing stubborn fixings, eliminates skinned knuckles, can help you earn more money AND have more time to spend with your family and friends. Having read this article, you're in the perfect position to read our impact wrench reviews and find the tool that meets your exact requirements.