What's an Impact Driver, and How Does It Work?

What’s better, acquiring tools or speed parts? The preference depends on a multitude of factors, but, I personally get giddy when it comes to new-to-me tools, especially when it comes to power tools that make life a whole lot easier.

None of the power tools in my collection deserve higher praise than my impact driver. It’s a cheap model from a certain freight company that I’ve used and abused for virtually any project I’ve taken on since acquiring it. The impact driver is an undisputed garage champion thanks to its power, versatility and durability. 

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Its usefulness comes down to its function. Impact drivers are a little more tool than a fancy drill and a little less tool than an impact wrench. Today, The Drive’s top tool nuts will break down exactly what that means by exploring what an impact driver is, what it’s used for, and why it became my go-to device. 

What Is an Impact Driver?

To understand impact drivers, you must first understand the purpose and functionality of drills.  

One of the primary purposes of a drill is to drive fasteners into materials. The use of rotational force provided by the motor and the pressure you supply with your hand makes this possible. Pretty simple, right? But what if the material is dense and tough to drill into? What if you hit a knot or a hard spot in the wood while you drill? Or what if a long faster has too much drag? You might think to simply add more pressure, but that’s not always the best idea. The problem in doing so is that you end up overloading the motor, bogging it down, and risk damaging it.

An impact driver is designed to solve exactly these types of problems with a two-pronged attack. Impact drivers use motors that supply more significant levels of torque than a drill and they use an impact action that helps to drive fasteners through more rigid materials when under load.

If that sounds familiar, it’s because that impact action is similar to the function of an impact wrench and a hammer drill. In comparison, impact drivers aren’t as powerful as impact wrenches and hammer drills, nor are they as precision friendly as a power drill. However true that may be, the result of the design is a tool that lands somewhere in the middle of all three. You wind up with a tool that can be used in various settings with a compact size that compliments all projects.

Here we can see the impact mechanism between the motor and the collet. 

How an Impact Driver Works

The power created by an impact driver might seem like a minor miracle, but these helpful tools rely on reasonably simplistic mechanisms. The internals looks very much the same as a drill in that you have a motor that applies rotational force. Only it’s more compact to allow room for the hammer and anvil.

Just like with a drill, there’s an output shaft. Only before the output shaft reaches the chuck or collet, in this case, there’s an additional mechanism that’s composed of a spring-driven hammer and anvil.

A closer shot of the spring and hammer that supply impact. 

Until enough load is applied, the spring forces the hammer against the anvil, which allows it to act just like a drill. The magic happens once the fastener provides enough opposition.

The hammer can cam away from the anvil and depress the spring when the system is under load. After it clears the anvil, it snaps back into position and spins freely until it strikes the anvil again. The collision of the hammer against the anvil creates the impact action. That impact supplies the force for the system to continue to drive a fastener into place.

Here we can see the anvils that the hammers strike to supply the impact action.

This system replicates the action of striking a wrench with a hammer just on a much smaller scale.

Why Is the Impact Necessary?

The impact function is crucial for driving fasteners through hard materials, but that’s not the only time it comes in handy.

Say you’re driving fasters in a tight spot that you can’t get a drill in, nor can you apply much pressure because you’re at an awkward angle. The impacting action helps to drive the faster through whatever you need it to. It also delivers a shock that helps to free stubborn fasteners that a drill will struggle with.

You may be able to use a normal drill for either setting, but you can run into several issues. As we already said, applying too much force bogs down the motor and can ultimately kill your drill. Not only that, but the increased pressure is also hard on your wrists, which is never a good thing during a long day of wrenching.

What Makes Impact Drivers So Versatile?

The impact action and rotational force created by impact drivers allow the tool to be used for many things. But perhaps what truly boosts its versatility is that quick-change drive attached to the head.

Most impact drivers feature a quick-change collet that accepts bits that feature a 1/4-inch hexagonal shank. Drill bits, bit drivers, and all sorts of other goodies can hook right into this slot, allowing you to get to work on anything. Heck, you can even get a keyed-chuck with a 1/4-inch shank that will enable you to use standard drill bits in there. Again, it’s not as precise as a regular drill, but it comes in handy when you need to quickly put a hole in something.

Beyond that, possibly its most helpful feature is that it works with socket adapters that essentially turn your impact driver into a mini-impact wrench. Factor that in with everything else, and you can see why an impact driver comes in handy for virtually any project around the shop.

Impact Wrench on the left, impact driver on the right. Choose your fighter.

Impact Drivers vs. Impact Wrenches 

Before we get ahead of ourselves, we should explain the differences between an impact driver and an actual impact wrench.

The most significant factor is that an impact wrench is a dedicated tool that features a permanently mounted ¼-inch, 3/8-inch, or 1/2-inch socket drive. And because impact wrenches are explicitly intended for dealing with stubborn nuts and bolts, they’re generally far more powerful than impact drivers. 

Because of this, an impact driver does not take the place of an impact wrench. The 1/2-inch socket adapter available for your impact driver will likely see little to no use because they generally don’t provide enough power to break large hardware free.

Again, size says it all. Here we have a side-by-side comparison of the striking mechanisms used to generate impact. 

Again, the primary purpose of an impact driver is to drive fasteners through harder materials. Being able to free nuts and bolts is something of a byproduct.

Can I Use an Impact Driver on My Car? 

Because you have the ability to attach sockets to your impact driver, you absolutely can use them for automotive projects. But don’t expect it to perform as well as an impact wrench that’s intended for this line of work.

Your working experience with an impact driver in this setting depends on the model you choose. That’s simply because some are more powerful than others. But because many fasteners are set in place with ample amounts of torque, it’s almost a guarantee that you’ll still use a wrench to break nuts and bolts free then use the impact driver to take it home.

Mjolnir, we mean a Milwaukee Impact Wrench. 

Now, don’t rule them out just because impact wrenches typically bring heaps more torque to the table. Something to love about impact drivers is that they aren’t overpowered to the point where you’re always worried about stripping threads if you choose to use them to tighten something down. While it’s never wise to use an impact for tightening, you can (at your own discretion) get away with using impact drivers to gingerly set hardware in place before torquing.

Furthermore, the ability to use one as a drill makes them an excellent choice for driving sheet metal screws and other miscellaneous tasks. Again, a drill is superior when precision is of utmost importance. However, the lightweight and compact design of impact drivers paired with higher torque output make them perfect for a variety of automotive-related tasks.

In short, an impact driver isn’t the perfect tool for every job, but its versatility makes it a great addition to any mechanic’s tool collection.

Types of Impact Drivers

It’s easy to come to the assumption that all impact drivers are the same, especially when the market is dominated by cordless impact drivers. Although it does make sense that consumers prefer battery-powered impact drivers due to their convenience, it’s not your only option. That said, let’s talk about the different types of impact drivers that you have available to you.

Corded

Corded impact drivers aren’t as easy to come across, but they do exist. Rather than relying on a battery, these variants tap directly into a power outlet. The obvious pro is that you don’t need to worry about charging the battery or keeping a spare around to prevent any hiccups. The drawback is that it can work against the convenience factor of the compact design. The length of the power cord and fumbling with it can make it very difficult to work in tight spaces. 

Wireless

Cordless or battery-powered impact drivers are by far the most common variant. Without a cord snagging on the car or anything else in the garage, they are far easier to use in any setting. It’s important not to assume that all cordless options are the same, though. Different lines offer different levels of power, and you’ll even see that you generally have two different sizes to choose from. While the traditional layout is already pretty small, there are compact models available to you. The compact versions aren’t as powerful, but they are a clear choice for workspaces that inspire claustrophobia. 

Pneumatic

Officially known as a “pneumatic impact screwdriver,” this type of impact driver is far less common in today’s electricity-driven world. These models offer all the typical benefits of an impact driver, only it relies on air pressure rather than electricity. Obviously, that genetic alteration does make them lighter and possibly more powerful, but it does mean you’re reliant on an air compressor to work. For more information about the benefits of an air compressor, visit our guide to pneumatic tools. 

Manual

A manual impact driver is not a power tool, but it’s worth mentioning. On these tools, the system relies on you attaching a bit to the driver’s nose and striking the rear of the tool to create rotational force. At a very base level, it’s like using a hammer and chisel. 

They aren’t great for extensive jobs that can be handled by the types mentioned above, but you can create a tremendous amount of force that’s necessary for releasing particularly stubborn hardware. And it’s always good to have a manual backup in case all of your batteries die.

FAQs About Impact Drivers

You’ve got questions, The Drive has answers!

Q: Can I use my impact driver as a drill?

A: Yes. Impact drivers are intended to take the place of a drill when driving long fasteners or dealing with harder materials. The quick-change collet allows the user to attach many different bits specifically intended for such a purpose. The thing to remember is that impact drivers are more powerful than drills. While that might seem like a good thing, it ultimately decreases the tool’s precision and increases the likelihood of stripping fasteners.

Q: Can you use an impact driver to remove lug nuts?

A: Not typically. While technological advancements are likely to create exceptions to the rules, impact drivers generally aren’t powerful enough to remove lug nuts. You can, however, use them to unthread lug nuts after they’ve been broken free by a breaker bar or tire iron.

Q: When should you not use an impact wrench?

A: You should not use an impact wrench any time precision is necessary for drilling holes or torquing down nuts and bolts. Impact drivers are meant to replace drills in certain settings, but the impacting action and increased power aren’t known for leaving behind the cleanest fit and finish. And because they are powerful tools, you don’t want to use them for tightening nuts and bolts down. Even though they aren’t as powerful as impact wrenches, there is still the risk of over-torquing and stripping threads.

Q: Should I buy an impact driver or a drill?

A: Both. While the impact driver is versatile, it’s not a drill. Drills are ideal for a project that requires total precision. So, if you’re putting the finishing touches on a project, a drill is the right tool for the job. However, if you’re trying to install long fasteners or drill into harder materials, an impact driver will make life a lot easier. Ultimately, these tools do things that the other can’t, meaning both have specific settings to perform in.

Q: Can you use regular sockets on an impact wrench?

A: You can. But the fact of the matter is that regular sockets are not designed to withstand the impacting action of the tool, and they are likely to crack or shatter under load. That said, you should use impact sockets for impact wrenches and even impact drivers. I’ve personally used regular sockets on my driver and never ran into such an issue, but there is the right tool for the job, and it’s best to use impact sockets for these applications.

Here’s a Helpful Video

We’re always on your side, and we get that most of you are visual learners. Not only that, it can be tough to put the exact workings of these tools into perspective without visual aid. This video not only provides a breakdown of an impact driver but does a great job at explaining how they all work together!

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We’re here to be expert guides in everything How-To related. Use us, compliment us, yell at us. Comment below and let’s talk! You can also shout at us on Twitter or Instagram, or reach us all here: guidesandgear@thedrive.com

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