There are many things to consider when purchasing an impact wrench and it’s important to choose the right one for the job you have. You need to understand how much power you’ll need, type of motor you want and any additional features that might be important. Once you know what type of impact wrench you need, you’ll still have many options to choose from. Since power tools are an investment and shoddy tools can sometimes cause painful injuries, make sure you choose an impact wrench made by a reliable manufacturer. Whether you are looking for a corded impact wrench or a cordless we will run you through all the key features to consider before buying.
What is an Impact Wrench?
An impact wrench (also known as an impactor, impact gun, air wrench, air gun, rattle gun, torque gun, windy gun) is a power tool that can be used to replace a manual socket wrench. The impact wrench has about twice the torque of ordinary wrenches. If you have a nut you can’t loosen with a socket wrench, an impact wrench can make easy work of it. This power tool replaces the manual labor of loosening and tightening fixtures by delivering high torque that is stored and delivered in bursts to an output shaft.
A standard impact wrench can accommodate 1/2-inch sockets of various sizes and should not to be confused with an impact driver, which has a 1/4-inch hex opening.
Uses for an Impact Wrench
If you’ve ever watched a NASCAR race, you’ve probably seen the pit crew using an impact wrench to quickly remove and then replace lug nuts as they changed a tire. Although this tool is commonly used for loosening lug nuts from cars and trucks, they can be used in any situation requiring high torque.
It’s not necessary to use an impact wrench when changing a tire, after all, you can use just a standard lug wrench. If you are looking to get the job done quickly and conveniently, the impact wrench will make it easy work.
How an Impact Wrench Works
There are many types of impact wrenches available, but they all work on the same basic principles. They begin by storing energy in a heavy rotating mass and releasing it all at once in small impacts against the output shaft. This puts an extreme amount of force on the bolt or nut that you are trying to loosen and removes the strain from your wrist had you worked manually. The release of the energy in small impacts creates a hammering action. For the most part, the bit stays still except for when it is periodically hit by the hammer internally as it engages with the output shaft.
There is a spring that pushes the hammer into the output shaft, creating the periodic hammering action. The hammering action creates a sudden, intense twisting motion in short bursts, normally about every five seconds. The continuous short, strong bursts of force trying to twist on the fastener are what eventually bring some movement, either loosening or tightening.
The short bursts of force provide much greater torque than you would be able to create using a regular socket wrench. This greatly reduces the amount of human effort needed and allows you to get the job done faster and with less risk of injury.
What to Look for in an Impact Wrench
Torque is the most important feature of an impact wrench because that is the definition of the amount of power it can produce. Torque can be measured for reverse and forward power and is usually stated as the maximum torque which is the maximum amount of torque that the tool is able to deliver in either setting. Keep in mind that torque capacity can change based on variables like bolt type and size, thread conditions, and air pressure. Because of these variables, there currently is no industry-wide standard for testing or publishing torque ratings that are consistent among the different manufacturers.
When shopping for torque, the advertised number may not be an accurate measure of the torque, but it can be used as a scale for the amount of power. Hence the more torque you need, the higher the number you should choose. As long as it has a rating greater than the required torque, you shouldn’t have any problems. Some impact wrenches have adjustable torque, giving you numbered settings that allow you to regulate the amount of torque.
No matter what type of impact wrench you select, you are going to need a socket set. You should never use an ordinary socket set with an impact wrench. Using non-impact sockets on an impact wrench is bad for the wrench itself and can cause the sockets to shatter creating an extreme safety hazard. Chrome sockets will actually wear down the shank of an impact wrench because the chrome is harder than the steel the shank is made from. Ordinary sockets are not designed to be used with a rotating load which causes them wear quickly and become oversized and slip. Impact wrench sockets are heavy duty and designed to grip at the attachment site to prevent them wearing, shattering, or damaging the impact wrench. Always use impact rated sockets.
Another useful accessory is a socket extension set. There are extension sets made specifically for impact wrenches. Theses sets include multiple pieces that extend the reach of your impact wrench for easier access in tight spots.
If you have decided to purchase a cordless impact wrench, you’ll want to make sure it comes with a charger and a battery. It’s often a good idea to have multiple batteries and even multiple chargers so you never run out of power. If you have many cordless tools by the same manufacturer, their batteries may even be interchangeable, but always check the manufacturer's recommendations.
Finally, safety equipment should not be overlooked. Safety glasses or goggles are strongly recommended when using a high-powered tool with a lot of torque. If a bolt breaks or comes off suddenly, or the impact wrench malfunctions, you could have a high-speed projectile coming at you and you want your eyes to be protected. Ear protection is also a good safety measure. The higher sound levels generated by some power tools, especially if used over extended periods of time, can lead to hearing damage which can be prevented by the use of earplugs or earmuffs.
Each type of impact wrench has its advantages and disadvantages, depending on the job at hand. For mechanics and other professionals, pneumatic wrenches have the best power to weight and volume ratio. If you are buying this tool for occasional home use, electric tools are a good option since they are less expensive. Cordless tools are the only portable option but tend to be larger, heavier and more expensive than air or electric units.
Tools help make jobs easier and the right tool for the job can save you hours and can even prevent repetitive use injuries. Investing in a quality impact wrench can make your time in the workshop or garage more enjoyable.