When it comes to driving screws into concrete you really only have two choices – a rotary hammer or a drill driver that can act as a hammer drill. Both tools have a similar mechanism that pounds the bit as it spins so that the concrete is destroyed and the screw can go in but they are not quite the same and that causes a difference in power and performance.
Several companies will tell you that their Hammer drills are strong enough to power through concrete, but you have every right to be skeptical about this as it’s one of the toughest tasks a drill like this could potentially face. Rotary hammers can be bulky and expensive if you’re not planning on using them regularly or have enough jobs for a tool this powerful.
In a rotary hammer the bit has a compressed air cylinder behind the piston which drives it forwards into the bit to create an impact, while in a hammer drill a clutch controls two metal disks beat back and forth onto the bit to create double the impacts. A hammer drill is usually found in consumer grade kits and while it’s more powerful than a drill/driver it’s still not as powerful as a rotary hammer.
The hammer is controlled by a clutch that allows the piece to hit at about 30,000 bpm which moves the chuck in and out. The in and out motion helps to break up the material which means it’s good for breaking up masonry and concrete but isn’t intended to drive fasteners. They have two direction modes depending on which way the chuck is rotating. This is intended for light duty use with holes up to 3/8” diameter.
The rotary hammer has better shock absorption and will provide a much harder impact to the bit. A rotary hammer does not have the same motion at all as the hammer drill. Rotary hammers use carbide bits that have special shanks to hold them in place and only have three modes – drill, hammer, and hammer drill. The air cylinder and piston combo has a longer stroke than the clutch system which means that there are less hits but they are more powerful.
Depending on how powerful the hammer is this may be a single piston or several. Larger rotary hammers may use crank-type pistons instead of air filled, these have an inner gear mechanism that moves the pistons. Hammer mode allows the tool to have a chiseling or scraping motion as well as a rotation for fastening. The most popular attachments include clay spades, cold chisels, tile remover, bull point chisels and scaling chisels.
A rotary hammer can handle holes of up to 2” in diameter while the drill only mode will allow it to be used on masonry like a hammer drill without destroying the concrete completely. This is usually use by contractors and professionals since it has the option to have extra power using the hammer function if needed.
The most noticeable difference other than mechanism is that the rotary hammer can weigh up to a hefty 18lb, almost 5 times as much as the average hammer drill. The average hammer drill will cost you between $50-200, and it’s shelf life is between 1-2 years with moderate to light use. The Rotary hammer on the other hand will cost you between $150-300 or more depending on the brand and the power.
The hammer drill has a simple chuck that can swap out between drill bits and fasteners. These are usually impact grade to be sure that they can withstand the impact of the disks onto the driver but regular ones will work for light duty jobs. The rotary hammer on the other hand has a completely different chuck system. A rotary hammer has a much more efficient SDS chuck with a slotted drive which prevents bit slippage.
The SDS term was originally developed by Bosch to determine what sort of load the bits can handle. SDS max, for example, is meant for heavy duty masonry and are incompatible with other bits because they have an 18mm diameter, these bits have 4 times the cross section shanks of regular bits. SDS/SDS+ have 10mm diameters and are interchangeable.
Head to Head
Bosch 11255VSR BULLDOG Xtreme 1-Inch SDS-plus D-Handle Rotary Hammer
Rockwell ShopSeries RC3136 7 Amp 1/2-Inch Hammer Drill
Bosch Rotary Hammer Rockwell Hammer Drill
Modes 3 (variable speed) 2 (variable speed)
Weight 11lb 6.5lb
Amps 7.5 7
Volts 12 18
Chuck Keyless ½”
RPM 1300 2800
BPM 5800 44800
Added Features Lockable rotating 36 position chisel Turret handle for better control
Holes in concrete in 3 Minutes 40 8
For Up to $100
You’ll find basic hammer drills that have motors between 6-8A. These will be good for basic light masonry, bricks and mortar with holes up to a 1/2” diameter. While they can drill into concrete it’s slow going and there’s a good chance you’ll hurt yourself or burn the motor.
For $100 up to $150
You’ll get a little bit bigger motor up to 10Amps which can push holes up to 5/8”. This will take on concrete but not heavy duty concrete or reinforced. This would be the maximum for most hammer drills as anything more you’re either paying for the name or a lot of accessories.
For $150 up to $225
This is the range most rotary hammers will fall into. You’ll have about the same 7-10 amps of power that the higher hammer drills have but you’ll also get up to 3ft.lb of impact energy which adds considerably more push. This is good for quickly drilling holes in masonry and concrete up to 1”. It can be used for chiseling tile, busting small concrete and removing mortar. You may find one or two hammer drills in this range but it’s unlikely they will be worth the money.
For over $225
This is for heavy duty use and projects. These generally have an impact energy of over 10ft.lb and can drill 1-3/4” holes consistently all day. You’re likely going to be paying a minimum of $400 but if you don’t need one other than sporadically consider renting one instead for around $50 per day. You will not find any hammer drills this powerful or in this price range.