The impact driver. Could you get by without one, just relying on a drill driver? We suppose, but then one would feel a void in one’s life. How do we best describe the awesomeness of this power tool? Think of when you’re finishing that plate of wings and you need to clean up. Your fingers are messy, but blessedly, there, on the table, are a bunch of wet naps. Could you use a napkin and some water to wipe your hands? Maybe, but while it gets the job done the napkin tends to shred. Could you go to the restroom to wash up? No way, you can barely move after that plate of wings. But there is that wet nap calling out to you. If you’re able to peel apart the wrapper then cleaning up is a cinch. And your hands are so clean when you’re done that you should reward yourself with another wing. Go for it, cleanup is easy.

So it is with an impact driver. It’s just so much easier to use an impact driver to driver fasteners than it is to use a drill driver. Impact drivers are particularly good at driving long screws into hard wood, as they generate incredible torque for their size. While it’s true that many impact drivers don’t have a clutch disengagement mechanism to prevent driving too deep, there are very, very few disadvantages to using an impact driver.

Impact drivers work by using an impact mass inside the driver to hammer into the wings of an anvil connected to the driver shaft and to deliver a controlled jolt of high torque that turns the bit. Fine Homebuilding has a pretty good video on the innards of an impact driver. An impact driver will produce more torque than a similar sized/powered drill driver and have less of a tendency to cam out of a fastener. There is also less of a reactionary force (remember Mr. Newton’s laws) produced by an impact driver because of the short duration of the impacts, so it’s easier to hold an impact driver with one hand and not have it twist away from you. Do not be confused to think that an impact driver delivers a downward force like a hammer drill does. Impact drivers deliver torque.

One big drawback is that impact drivers are very loud. The sound of the impact mass hitting the anvil 50 times each second is noisy. Wear ear protection. The first time we used an impact driver we thought there was something broken inside the driver, but it’s actually supposed to make that much noise. That’s the price paid for all that extra torque generated.

Impact drivers tend to be shorter than drill drivers in both length and height. This is because impact drivers are typically one speed and don’t need the multi-speed clutching mechanism that many drill drivers have and therefore the chucks are shorter.

A note on using an impact driver to drill. You can do it, but it’s not the same using a hex bit to drill with than it is using a regular bit gripped in the chuck of a drill driver. When the impact action starts the accuracy of the drilling starts to decline. We would not use an impact driver when drilling holes for fine carpentry.

Cordless vs. Corded Impact Drivers

The majority of impact drivers are cordless. There are a few that are corded, and some that are powered by compressed air (but most pneumatic impact tools are impact wrenches, commonly used by auto mechanics to loosen and tighten nuts and bolts). We don’t recommend getting a corded impact driver. Get a cordless one and always have an extra charged battery at the ready. It’s not worth it to invest in a corded impact driver. If you run out of juice in your cordless impact driver then switch to your corded drill driver until you can recharge, and smack yourself for not having that extra battery ready. With lithium-ion batteries that are popular today, it’s best to use the tool often and immediately recharge the battery when done, as lithium-ion batteries like a regular charge and discharge cycle.

Impact Driver Features

Here are features to consider when purchasing an impact driver.

Chuck

The chuck holds the bit in the impact driver. Unlike drills, impact drivers don’t have three jaw adjustable slip chucks, but instead quick release hex chucks. You push the chuck collar forward to fit a new bit in or release one already in the chuck, and then release the chuck which gets pulled back by a spring. The quick release chucks on impact drivers are typically 1/4″. You use 1/4″ hex shank bits in the chuck.

Power

Cordless impact drivers are rated in volts. All else being equal, impact drivers rated with higher volts will be more powerful and also heavier and more expensive. Impact driver voltages range from 9.6V(olts) to 20V. The thing to remember about impact drivers is that they deliver a lot of torque, so 12V models may deliver as much torque as you need. 12V models are small and lightweight and will let you drive long screws in hard wood, although it may take longer than using an 18V model. We’d recommend 12V impact driver models except for the fact that we recommend 18V drill drivers, and we want to use the same battery system across cordless tools. Therefore, we recommend getting the impact driver that matches the drill driver you select. 18V impact drivers aren’t that much bigger than 12V impact drivers, and you will get a longer runtime with 18V impact driver models vs. the 12V models.

Smaller voltage impact drivers may generate around 700 pound-inches of torque, while larger voltage ones up to 1500 pound-inches or torque, or about three to four times the torque generated by comparably sized drill drivers.

Speed Settings

Some impact drivers offer speed settings, but we wouldn’t say that it’s a common feature yet. The speed settings let you set the rotational speed (RPMs) and the number of impacts made on the anvil (IPMs). RPM settings may be around 1400, 2000 and 2600 RPMs, and IPM settings may be around 1400, 2800 and 3400 IPM. The lower settings are for smaller fasteners. Here’s the thing though, even at the lowest settings, impact drivers produce a lot more torque than drill drivers, and they don’t have a clutch mechanism like drill drivers do to prevent over sinking of screws. You can control the driving by watching closely and using the trigger nearly equally as well at high or low speed settings, and even at the low setting an impact driver isn’t good for precision driving of small screws. We don’t think that multiple speed settings are very valuable, considering the primary use of impact drivers is to drive screws into tough, hard wood, and that driving is a slow process.

For single speed impact drivers, you’ll want one that’s rated at least 2000 RPM

Battery, Charger and Recharge Time

Lithium ion batteries are superior to nickel cadmium and nickel metal hydride . A smart charger will recharge the battery in as little as 15 minutes, and typically in under an hour. It will adjust the current as necessary for optimal charge time and battery life. You will want a battery with a meter that indicates remaining charge. This is important for lithium ion batteries as you should not fully run them down. Lithium ion batteries with 3+ amp hour ratings are the most desirable, and will take the longest to charge.

Reverse Switch

We haven’t seen an impact driver that doesn’t have a reverse switch. It’s a must have. The reverse switch should be easily reachable from the handle/grip and ideally be able to be switched with one thumb or finger (or knuckle or arch).

Built-in LED Work Light

Having a built-in work light is handier than you think. Even if you think you’ll always be working in bright light, there will be times when you’re in low light and you’ll appreciate the built-in light illuminating what you’re targeting.

Grip/Handle

An impact driver’s handle is usually in a T configuration. The T-handle is underneath the drill, balancing the weight of the impact driver and making it easier to wield. Impact driver’s are lighter than drill drivers, so you should find them easier to use, even 18 or 20V impact drivers.

As we mentioned, the reactionary force of an impact driver is less than that of a drill driver. This is because the impact driver doesn’t produce constant torque, but rather ultrashort bursts of high torque. What this means is that if the bit gets stuck when turning, the impact driver won’t wrench itself out of your hand like a drill driver would.