How to Use an Impact Wrench

Jul 24, 2023

Why any grease monkey needs an impact wrenches in his toolbox: they make removing lug nuts a quick and easy task.

Impact wrenches are found in the tool chests of mechanics everywhere. They're commonly used for loosening lug nuts from cars and trucks, but they can also be used in any high-torque situation.

Not to be confused with an impact driver, which has a 1/4-inch hex opening, a standard automotive impact wrench can accommodate 1/2-inch sockets of various sizes, including those that can fit a wheel lug.

Impact wrenches have traditionally been as pneumatic-powered tools, similar to the types used on pit road during auto races. The loud whirring sound is their signature and still the most commonly used tool in professional garages. But cordless 18V impact wrenches are now readily available and have the type of power to loosen lug nuts that are roughly tightened at 100 feet of torque. They are also still extremely loud so hearing protection should be worn when using them.

Impact wrenches get their immense torque from a hammering mechanism in the tool that delivers strong concussive blows extremely quickly. When loosening a lug nut you'll notice the socket attached to the impact wrench moving slowly as the lug nut is loosened and then quickly when it's loose. Be cautious when tightening lug nuts using an impact as it's easy to over torque them—which can stretch or even strip the threads.

A standard lug wrench is all that's needed to remove a tire, but if you are looking for speed and convenience (and, let's face it, a chance to pretend like you're in a NASCAR pit crew) get an impact wrench.

Timothy is a lifelong DIY enthusiast who is fixated on smart home tech, beautiful tools, and wrenching on his FJ62 Land Cruiser. He’s the DIY editor at Popular Mechanics and also the founder of the home improvement site, Charles & Hudson, the Webby-nominated family site, Built by Kids, and Tool Crave. When not working, you’ll find him on his board or bike enjoying the LA weather with his family and friends. Follow him on Instagram and Twitter.

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