There are occasions when a standard drill simply will not suffice. When building a surface ledger against a concrete base, for instance, you’ll need a more advanced tool to drill a lot of holes. That’s when you’ll need a rotary hammer or a hammer drill. Although the names are sometimes used synonymously, the methods are not the same.
A rotary hammer is a heavy-duty device that works more like a jackhammer than a typical power drill, whereas a hammer drill is a less-advanced machine which can also be used to drill into metal or wood. Each one is discussed in greater detail below.
Hammer Drill
A hammer drill’s hammering action is delivered by a sophisticated clutch mechanism comprised of two ridged metal disks (or gears). The ridges travel up and down as the disks rotate against each other, causing the chuck to pass in and out. As a result, when rotating, the drill bit goes up and down. The bit moves a short distance, and the hammering motion is swift and shallow—up to 30,000 BPM.
One advantage of a hammer drill over a rotary hammer is that the pummelling mechanism can be turned off. You can go from drilling in a concrete block to drilling into wooden frame with the push of a button and the switch of a bit. When operating on poured concrete, these tools will typically use a 1/4-in.-dia. piece. In masonry and block, a 3/8-in.-dia. or smaller bit may be used.
A hammer drill is typically larger and heavier than a traditional drill due to the physical mechanics required to create the pummelling action. Having said that, many of today’s hammer drills are really not that different in form and size from conventional drills. One distinguishing characteristic of a hammer drill is the use of a standoff handle to hold the tool steady.
Rotary Hammer
A rotary hammer drill is the weapon of choice for larger holes. A rotary hammer generates hammering action by compressing air and moving a striker. The blows are delivered at a slightly slower pace than a hammer drill, but the impacts are much more intense. Consider the hammer drill to be a sledgehammer, and the rotary hammer to be a haymaker. The rotary hammer’s strength means less work for the operator, but it also implies that it is not ideal for use on metal or wood.
Unlike hammer drills, which usually have a regular adjustable chuck, rotary hammers have a spring-loaded screw that correlates directly to the size of the bits in use. A rotary hammer, unlike a hammer drill, can be turned to hammer-only mode. This is important for light demolition tasks like tile removal. A rotary hammer, on the other hand, doesn’t even have a drill-only mode.
Rotary hammers allow you to tackle larger tasks and demand less effort on your part. A rotary hammer is important if you’re drilling 3/8-inch or larger holes in masonry, smashing up concrete, or drilling into rebar. The extra power, however, does not come cheap. Buying a rotary hammer may be overkill if the job does not require it. If you’re looking doing some light woodwork or just small home maintenance projects, a hammer drill would possibly serve you well.
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