What Is a Hammer Drill and What Is It Used For

Worker with Hammer Drill

Have you ever drilled a hole into concrete or stone, e.g. to hang a picture or a cabinet? If so, you have likely come across a so-called hammer drill.

A hammer drill is a power tool that is used for drilling holes in hard materials such as brick, concrete or other cement-based objects. Hammer drills are also known as percussion hammer, impact, or pneumatic drills. They have a mechanism that generates a rapid hammering action driving the drill bit back and forth in short thrusts which pulverizes the material that is to be drilled.

Practically, non-hammer drills or rotary drills can also be used for drilling into hard materials. However, they are less effective than hammer drills and probably would not work at all on the hardest material.

Most hammer drills, on the other hand, have a switch that can turn the hammering action on or off. Thus, they can also be used for screw driving or drilling other softer materials such as wood in the same manner as a normal rotary drill.

Inside a standard hammer drill, there are two sets of toothed gears that mechanically interact with each other in a cam-type action. This produces a hammering effect when the chuck is turning. The toothed gears are either in the drill itself or in the chuck, depending on the type of hammer drill.

There are three basic types of hammer drill that we will be covering in detail: rotary hammer drill, percussion hammer drill and pneumatic drills (source)

Rotary Hammer Drill


A Hilti Rotary Hammer Drill.
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this one and other rotary hammer drills on Amazon.

What Is a Rotary Hammer Drill

This drill’s hammer action is produced by a technology called “electro-pneumatic” hammering. There are two pistons inside the drill, a drive piston and a flying piston. The drive piston is moved back and forth inside a cylinder by an electrically powered crank. The flying piston is located at the other end of the cylinder and its movement caused by compressed air inside the cylinder generates the hammering action. This method is far more practical and compact than using an external air compressor.

Slip clutches are used inside rotary hammer drills to protect the drill and operator should the drill stop suddenly. In such an event the slip clutch disengages and stops the drill otherwise violently wrenching which without happen without the clutch.

They have such force that standard masonry bits would not be held tight enough to sustain such hammering action and would quickly be shaken from the drill’s chuck due to their smooth shank. Special bits which have a set of grooves in the shank have therefore been designed for rotary hammer drills. The groove marries with the drill’s chuck and locks it into place.

A switch enables the user to change between hammer drilling or hammer action only without the drill bit rotating. This second function allows the drill to be used as a chisel in a similar manner as a jackhammer.

What Is a Rotary Hammer Drill Used For

A rotary hammer drill is designed for heavy-duty work and is commonly used in the construction industry. They can be used for drilling and also chiselling cement or brickwork and use a piston mechanism instead of toothed gears. The piston mechanism enables this type of hammer drill to deliver a much more powerful blow enabling larger holes to be drilled quicker.

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Percussion Hammer Drill / Impact Drill


A Dewalt Impact (Hammer) Drill.
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this one and other impact drills on Amazon.

What Is a Percussion Hammer Drill / Impact Drill

Percussion hammer drills are also known as impact drills or just simply, Hammer drills. They are smaller in size than rotary hammer drills and are the most common type of hammer drill that a DIYer is using.

The hammering mechanism inside is caused by two sets of toothed gears rubbing together in a similar way as a clutch but the teeth cause the rotating action to be turned into a hammering action. There is a switch that can turn the hammering function on or off so the drill can be used as a conventional drill or power screwdriver. Percussion drills use standard masonry drill bits that have a smooth shank. Although it is also possible to use a fluted drill designed for a rotary hammer, the flutes mean it is difficult to hold the drill bit tightly and it may shake itself loose.

What Is a Percussion Hammer Drill / Impact Drill Used For

These hammer drills are rather used for the occasional hole for things like wall plugs, anchor bolts or concrete screws. In general, Impact drills are not normally used in the construction industry but they are practical for professionals and DIYers that may need to drill into different types of material, wood, metal or cement. A typical professional user might be an electrical who needs to mount electrical boxes: thanks to the versatility of his power toll, he can do so onto concrete with the hammer function enabled, or onto wood or steel with the hammer function disabled.

Check latest deals for impact drills on Amazon.

Pneumatic Drills


The TR Industrial TR89305 Jackhammer.
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this one and other pneumatic drills on Amazon.

What Is a Pneumatic Drill

Pneumatic drills are also known as Jackhammers or Kangos. They operate by forcing an internal hammer up and down to repeatedly strike the back of the chuck. Their effectiveness is dependent on the amount of pressure used by the operator. More pressure applied means the internal hammer hits the plate harder causing more force to be delivered to the bit.

Pneumatic drills differ from rotary and percussion drills in the fact they are not rotary and only a hammer action is delivered to the bit. They also differ in the fact that they are usually powered by compressed air. They are designed for more heavy-duty work and typically are used to break up large areas of concrete or rock.

There different Pneumatic Drill models, of which we will introduce the electro-pneumatic Hammers and the hydraulic drills.

What Is an Electro-Pneumatic Hammer Drill

There are some pneumatic drills that are electrically operated. These are called electro-pneumatic Hammers and have an electric motor that operates a crank driving two pistons in a similar way as a Rotary Hammer drill however they are usually considerably larger and more heavy-duty.

What Is a Hydraulic Drill

The largest type of pneumatic drill is a Hydraulic Drill. These are usually fitted to mechanical excavators or other similar large plant machinery and mostly used for demolition or construction groundwork. They are known as “Rig Mounted” or “Machine Mounted” breakers.

As they are fitted to vehicles that are massive enough and powerful enough to exert the forces required, they can be used on flooring, walls or even ceilings.

What Is a Pneumatic Drill Used For

Because of their weight and size, they can only be used to break up floor-based items. They are normally too heavy to be used on walls or vertical surfaces unless used by two very strong people, one person holding the pneumatic drill in place and a second person operating it.

The hydraulic drills are mostly used for harsh jobs like the demolition of houses. Similar machines are also used in the mining industry (source) where large amounts of material need to be removed by a machine that does not pose any risk of electrical sparking which in turn could cause an explosion if gases built up underground.

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Rotary Hammer Drill vs. Percussion Drill (Impact Drill) vs Pneumatic Drill – What Is the Difference

The Rotary hammer drill uses a piston mechanism rather than toothed gears. Thus, it is very effective when it comes to heavy-duty work: Its use cases are drilling larger holes into hard material and chiseling concrete, for instance.

A Hilti Rotary Hammer Drill.
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this one and other rotary hammer drills on Amazon.


Pneumatic drills or Jackhammers, on the other hand, are often used for breaking up stone or concrete structures. Examples of their typical application areas are demolition, construction and, for specific pneumatic drills, mining.


The Impact Drill (also called Percussion Hammer Drill) is likely the most common hammer drill among DIYers and homeowners: Whether you need to drill a hole into a stone floor or drive a concrete screw into a concrete wall to hang something, the percussion hammer drill is the tool of choice. When it comes with a hammer deactivation function, an impact drill can also entirely replace standard cordless and corded drills (although it tends to be heavier).

High-End DrillThe All-RounderThe Budget Choice
Example:
Metabo BS 18 LTX-3

Example:
Makita XPH12Z 18V LXT

Example:
SKIL 6445-04

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Other Considerations

Which Drill Chucks and Drills are Needed for a Hammer Drill

There are several different types of chuck available, depending on the required use and the type of hammer drill it will be used with.

For the serious DIYer, an SDS-Plus chuck is most robust. It has grooves that lock onto the grooves of SDS drill bits. No tools are required to insert or remove the bits and many different bits are available for all sorts of various jobs including cold chisel bits for breaking concrete, tile remover bits for pulling ceramic tiles off walls and floors, scaling chisel bits for removing rust and weld spatter. Be aware of the fact that some of these bits can only be used with rotary hammer drills with the rotary function turned off.


Example of an SDS-Plus chuck.
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A regular chuck adaptor can be attached to an SDS chuck enabling the drill to use standard drill bits without the fluting on the drill shaft.

Chucks that use keys to tighten are generally more hardwearing than the keyless types but take longer to swap drills. Cheaper chucks are available that contain some plastic parts. Needless to say these might look nice when new but are not as durable as all metal chucks.

Hammer drill bits are normally available in two different types. A standard carbide bit works well for drilling into ordinary concrete but using a rebar bit would enable the operator to tackle any rebar encountered inside the concrete too.

Health and Safety

By their very nature, hammer drills of all types are noisy and cause vibration. Prolonged use can lead to the failure of blood to circulate within the fingers, a condition known as “White finger”. Pain and tingling may also be experienced in the hands which are due to the median nerve becoming compressed and is known as “Carpal Tunnel Syndrome”. Prolonged use may mean increased pain going up the arm and after extended operating periods, muscles in the thumb may start to waste away.

Some hammer drills now have built-in vibration reduction systems which help protect the operator from long term effects.

Ear defenders should be used while operating hammer drills to prevent hearing damage and Tinnitus. For instance, a jackhammer is capable of emitting noises exceeding 100db at two meters.

Conclusion

In this article, we have introduced the three generic types of hammer drills – Rotary Hammer Drill, Percussion Hammer Drill and Pneumatic Drills – and their respective uses and characteristics to you.

The Pneumatic drill is mainly used in professional demolition or construction, and less of a DIY tool. If you need to do demolition or chiseling work in your yard or inside your house, a rotary hammer drill is likely the right tool for the job. For a one-off project, you can rent one – if you use it frequently,  consider buying such tool yourself. Compare the different rotary hammer drills on Amazon.

However, if you are looking for a tool that helps you drill holes into stone or concrete, an impact drill, aka percussion hammer drill, is probably the best choice and might even replace a corded drill at the same time. Check out current deals and reviews of impact drills on Amazon now.

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