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?
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 (typically cordless-only)
- 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?
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.
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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. coughLike the rep. in this Sears Blue Tool Crew videocough.
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Robert
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
Andrew C
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.
Le DiRenzo
Would you be please answer a question for me? I have some rusty bolts to remove. I do not want to break the heads off of the bolts. Would I purchase a Hammer drill with adjustable torque? Would I just start low torque and try to loosen bolt with vibration? Then raise torque incrementally? Then use wrench?
Stuart
I would use hand tools. A wrench or breaker bar with gentle tapa with a mallet, or a hand impact tool would be a good place to start.
Karl
‘Rust Buster’ on it first, an hour later and start weakening.
Robert
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
Joe
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
Richard
I have a Bosch hammer drill (corded) that does NOT have an adjustable clutch. In fact, most larger, powerful rotary hammers do not have clutches. There may be some “do-it-all” hammer drills with clutches similar to cordless drills, but any heavy duty hammer drill for serious use in masonry will not have a clutch. It will drive a fastener until it breaks or the drill stalls. My Bosch drill can be switched to rotary drill mode only – no hammering. It can drive a deck screw through the deck and continue to drive right into and even below the surface of the joist below.
Stuart
Great point! My Bosch corded hammer drill doesn’t have a clutch either. I added a clarification into the post.
The comparisons here were mainly between cordless models, but I didn’t make such distinction clear enough. Thanks for pointing this out!
Patrick
I guess you’re talking softwood deck?
Tony
Is the impact driver good enough for screwing concrete screws or I have to use hammer drill?
Matt
You will have to pre drill first. A few years back I had some quality issues with my dewalt drill chucks and started using just a 1/4″ impact. Using a drill bit adapter I was able to do any project with that one tool that didn’t require a massive drill bit. The impact made short work of drilling into brick or concrete. To this day I use the impact for everything that doesn’t require absolute precision. Far more rugged and easier to use IMO.
Peter
I was happy to hear that you were able to drill into brick or concrete with your impact driver. Do you have any specific recommendations for which bits you use for these applications?
Steven
Which would you recommend for wood and metal works?
Stuart
A regular drill/driver plus an impact driver.
al allen
this site was very helpful
Gopi
Hi,
Sufficiently Enlightened
Doug
I just bought a cordless impact driver rather than getting a hammer drill thinking that I could kill two birds with one stone. I also bought a 3/8″ masonry bit. I compared drilling into a cement block with both a cordless drill and the impact driver and the drill actually did much better. Plus the bit wobbles quite a bit in the impact driver. Since the drill is variable speed and can be used as a driver, I’m thinking of just returning the impact driver and getting a cordless hammer drill.