In a reply to a recent deal post that mentioned both a hammer drill and impact driver, Steve left us a comment asking about the differences between the two. That’s a great question, one we have been meaning to address for a while now.
What is a Hammer Drill?
Typical Cordless Hammer Drill
A hammer drill/driver is a drill with a specialized “hammer” mode that is used when drilling into masonry such as brick, cement, and similar materials. The hammer mode can often be turned off so that the drill can be used as an ordinary drill/driver. The hammer drill capabilities do add a little to the weight.
Hammer Drill Summary:
- can drill into masonry and anything else a non-hammer drill can work with
- adjustable clutch to match power with application and fastener size
- multiple speed settings
- heavier, larger
- drill chuck that can accept wide variety of bit styles and sizes
- well suited for drilling holes and driving fasteners
And an Impact Driver?
Typical Cordless Impact Driver
Impact drivers are completely different. While hammer drills vibrate in a back and forth motion, impact drivers have more of a rotary impulse. When driving a light duty fastener, the impact driver will behave like a cordless screwdriver. But when higher opposing torque is encountered, such as when driving a larger or longer fastener, an impact mechanism is activated, and the tool applies a rapid series of rotary impulses. The quick impacts of the mechanism deliver huge amounts of torque that help drive in fasteners.
Another advantage is that impact drivers are non-reactionary. When encountering resistive torquewith a drill/driver, the tool may seize and twist in your hands. An impact driver will not.
Impact Driver Summary:
- 1/4″ hex bit adapter can hold screwdriver bits and other attachments
- can deliver high non-reactionary torque
- compact & lightweight
- impact-rated bits are required (or at least recommended)
- well suited for driving fasteners but can also be used for drilling holes (especially impact-rated hole saws)
Which One Do I Need?
A better question would be which do you need more? A hammer drill/driver can be used to drill holes in a wide range of materials and can be used to drive fasteners when used with a bit holder or appropriate power screwdriver bits. The downside is that hammer drills are larger and heavier than non-hammer drill/drivers.
An impact driver is more compact and often lighter, and is primarily used for driving in fasteners. It can be used to drill holes, and we actually reviewed a few impact-capable drill bits. But an impact driver’s main purpose is to drive in screws, bolts, and other fasteners.
A hammer drill will have an adjustable clutch so that you don’t over-torque and damage fasteners or screwdriver bits. Impact drivers do not have adjustable clutches, but Dewalt does offer an inexpensive impact clutch that does a great job at protecting smaller fasteners from being over-torqued and stripped, damaged, or sheared-off.
So it’s not a choice of one being better than the other, because they’re complementary.
Hopefully this clears things up. And don’t worry about not knowing the difference, even those who are supposed to be in-the-know get the two confused. *cough*Like the rep. in this Sears Blue Tool Crew video*cough*.
Even the best hammer drills cannot crank out the torque of that little impact driver. They’re downright amazing when it comes to that. I’ve had cases where the best drills couldn’t drive in that 3 inch deck screw. The impact driver on the other hand, makes it look like child’s play. In addition, the drill driver is more likely to damage the screw head in serious torque situations even if it could otherwise do the job.
If you’re drilling into masonry on something, there’s no substitute for a hammer drill. An impact driver is all but useless for that.
Robert
I think the answer is pretty simple- get a hammer drill if you need to drill into masonry or concrete. Get an impact drill for screwing in fasteners.
Many 1/2in chuck corded drills come with the hammer function. I think everyone should have a corded 1/2″ chuck drill because you can find them cheap and and lifesaver when you have to drill big or repetitious holes, so just make sure yours has an hammer function when you get it. You will probably hardly use it, but at least you have it.
I also think everyone should have an impact driver, even if its a small 12V one. The big advantage isn’t the torque, its how the torque is applied. Because of the impact nature of the drills, you can drive large screws without having to worry about the bit slipping and stripping the screw head. You also never need to apply any downward pressure to drive screws. Its a lifesaver when you need to drive long screws, but can be used for almost any screw.
With a corded hammer drill and an impact drill, I hardly use my standard cordless drill/driver anymore.
Andrew,
I agree about the corded drill. They’re a good value and can sit on a shelf forever with minimal maintenance. Even the most recent lithium batteries can only sit for so long before they call it quits. Batteries need to be used. A cordless tool is only as good as the batteries that power them.
In my opinion, a cordless drill with a hammer function can be too bulky anyway. It defeats a lot of the portability. That’s why we supposedly use them in the first place. My cordless drill is just a straight forward drill/driver without the hammer function. When I need a hammer drill, I bite the bullet and pull out my good old fashioned corded hammer drill.
Robert
If your gonna do a lot of masonary drilling buy a corded hammerdrill if only once in a bluemoon then buy a cordless hammerdrill as for the impact drivers greatest tool for driving in screws and lag bolts unlike the hammerdrill you feel no torque on hand when driuving in even the largest lagbolts try it with a hammerdrill and you will need two hands to keep it was twisting your grip