Q&A OF THE WEEK: “Can I Use An Impact Driver for Nuts & Bolts on Mechanical Work?”

Q: Can I use an impact driver to tighten and loosen bolts? I just bought a new DEWALT 20-volt impact driver for driving screws, but I see that it’s made to handle 1/4” hex screw driver bits for deck screws, not the square drive found on sockets for mechanical work. I was hoping I could use this tool with my socket set. Do I have any options?

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This 1/2″ drive cordless impact wrench (as opposed to an impact driver) has all the power anyone would need to remove even large, rusty nuts and bolts. This tool has saved me more than once from an impasse where a regular wrench simply could not remove a fastener.

A: The short answer is “yes” you can use an impact driver for mechanical work, but only for small bolts and nuts – 3/8″ or less. Although you could get adaptors that allow sockets fit into the 1/4″ hex of your impact driver (image below), there are a couple of you won’t find this works well.

impact driver with adaptor
The adaptor you see on top of this impact driver allows sockets for nuts and bolts to be driven.

The first problem with impact drivers for mechanical use is power. Impact drivers  are very powerful for driving wood screws, but a big old rusty bolt is a big challenge. In the world of mechanics, impact “wrenches” are like more powerful impact drivers and that’s what you see in the top photo of this article. They also already have a square drive on them to take sockets directly. If you like to do mechanical work, a cordless impact wrench like the ones in the photos here  is very nice to have. Just be sure to get a powerful one. The smaller units don’t pack that much punch.The Milwaukee (top photo) is the one I use in my own shop and it’s a beast. Lot’s of power and lots of run time. The DEWALT, below, is in the commercial auto shop of a friend of mine. I introduced him to cordless impact wrenches a few years ago and he hardly ever uses the air-powered equivalent that used to be the industry standard for years.

The value of an impact wrench has nothing to do with laziness, either. These tools don’t just rotate, but rather they rotate in a powerful pulsed way, imparting a kind of vibration to the rotation. This makes impact wrenches much better suited to removing seized nuts and bolts than any hand wrench. I’ve run into severely corroded nuts and bolts in the past, and while it was completely impossible to remove them with a wrench (even with an extension pipe to make the wrench handle longer), a second or two with an impact wrench and they come right off. It’s enormously helpful.

This well-used DEWALT impact wrench is in the auto shop a friend of mine owns. Tools like these are now a mainstay of professional mechanic works.

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