The Difference Between a Drill, an Impact Driver, and a Hammer Drill

As you build your DIY toolkit, you’ll quickly discover there’s rarely just one version of any given tool. Of course there are Phillips head and slotted screwdrivers, but even hammers—possibly the simplest tool of all—come in a surprising range of varieties designed for different tasks.

When it comes to power tools, the differences can be more complex to suss out. Take drills: When starting out on a job, how do you know if you need a standard power drill, a hammer drill, or whatever an “impact driver” is? While you can get pretty far in your home maintenance career without knowing the difference, but there will come a point when using the right tool for the job will make your life a lot easier. If you’ve managed to get through life without knowing the difference between a drill, a hammer drill, and an impact driver, here’s the rundown you need.

Drills vs. impact drivers vs. hammer drills

Drills, impact drivers, and hammer drills are all used to drill holes and drive fasteners, but they work in different ways and are well-suited to different tasks:

• Drills are the easiest to understand, conceptually: Your trusty power drill spins the bit, delivering consistent, constant torque at a variety of speeds. When the motor encounters resistance, it disengages. That means that when your drill hits its limit, there’s not much more it can do to drive a fastener or bore a hole. A standard drill is good at both drilling and boring holes.

• Impact drivers also spin the bit and provide consistent torque—until the driver hits resistance. Then it adds a rapid, perpendicular, concussive force that temporarily increases the torque beyond what a standard drill can do. If you’ve ever hit something on the side with a hammer to loosen it, or clamped a wrench in place and hit the handle with a hammer to get a stuck bolt moving, that’s what’s going on here, but it’s happening dozens of times a second. The impact driver doesn’t have a clutch and will keep working even when it hits resistance. It’s usually pretty loud, and the vibration involved can tire out your hands and arms. As a result, an impact driver isn’t great for drilling—it’s best used to drive fasteners.

• Hammer drills operate like a standard drill, but when they’re in hammer mode (which you have to select), they deliver a downward-driving force (like a hammer hitting a nail) as opposed to the impact driver’s horizontal force. Hammer drills can operate like a standard drill if you disengage the hammer function—and like a standard drill, the motor will disengage when it hits resistance. A hammer driver in hammer mode is best for boring holes in tough materials, but not driving fasteners.

How to choose between a drill, impact driver, and hammer drill

Knowing how each of these tools works makes it a little easier to decide when to use one over the other. In general, here’s when to use a drill, impact driver, or hammer drill on your project:

• Drills are precision tools that are ideal for driving small fasteners like standard screws or boring holes into softer materials, like wood or drywall. It’s an ideal general tool for most small-scale DIY projects, and when you need more control over the driving or drilling action.

• Impact drivers are best used on denser materials, like very hard woods, or with larger or longer fasteners that require a lot of power to drive home. If you’ve ever tried to drive a long screw with a drill and discovered that it becomes frozen halfway through, that’s when an impact driver might be the answer.

• Hammer drills are best for drilling or fastening in very hard materials like stone, concrete, or brick—in fact, you should avoid using hammer mode on lighter materials, because it can cause damage. But because you can disengage the hammer function on most hammer drills and use them as standard drills, they can be a good multipurpose choice.

One final difference: Hammer drills and standard drills use a chuck that can accept a variety of bits, but an impact driver will only work with 1/4-inch hex-shaped bits.

Which one you should buy

Since a hammer drill can also be used as a standard drill, it’s the best option if you’re not sure which tool you should get or you want to avoid buying an additional tool for a future project—it gives you both standard drill capabilities and the added power of the hammer action. You can hold off on picking up an impact driver until you tackle a project that actually calls for one.