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.
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.