The Bosch hammer drills for do-it-yourselfers

A man removes tiles from a wall with a green Bosch hammer drill. — The hammer drill - your friend and helper when the going gets tough.

Hammer drills, also known as rotary hammers, are heavy duty powerhouses among DIY tools like drills and screwdrivers . Keep reading to find out how they differ from impact drills and how to use a hammer drill correctly.

When it comes to drilling holes into hard materials, hammer drills are the tool of choice. Among other drills and screwdrivers, nothing penetrates concrete surfaces like a Bosch hammer drill. And even when a hammer drill reaches its limits, a rotary hammer can step up and do the job! Plus, if you need to cut slots in walls or chip away at tiles, hammer drills are the ideal choice!

Hammer drills: what you need to know

So, what is a hammer drill? Let’s take a look at what you should know before buying an electric hammer drill, so you can get the best model for your DIY needs.

How does a hammer drill work?

There is one basic difference between an electric hammer drill and a “normal” drill. A standard cordless drill - with the appropriate attachments and bits - can cut holes in wood, stone, and metal.

By contrast, a good rotary hammer drill uses powerful blows to crumble almost any kind of material - the hammer drill bits usually only serve as a means of letting the dust out of the hole, as opposed to aiding the drilling process.

How do hammer drills generate the impact needed for drilling?

Well, that depends on the type of hammer drill. There are hydraulic machines that use oil pressure to work, and pneumatic drills that operate using air pressure. Our hammer drills function using an electric motor and a pneumatic percussion mechanism, which are also known as rotary hammers.

The drilling mechanism in a pneumatic hammer drill works like this:

The machine's motor drives a piston that compresses the air in a chamber.
This creates pressure, which then acts on a second piston (known as the flying piston) and thrusts it onto a firing pin.
This then transfers the force to the tool in the head, such as a drill bit or a chisel.

Advantages and disadvantages of rotary hammer drills

Rotary hammer drills are designed for specific tasks, meaning they have specific pros and cons.

Advantages	Disadvantages
Rotary hammers can act as both a drill and a chisel. They speed up the working process for hefty tasks. They are ideal for hard materials like concrete and stone. They require little manual effort.	Rotary hammers are great for versatility, but this means precise drilling isn’t possible. They are relatively heavier than other drills.

Technical features of a good hammer drill

Hammer drills vary in performance, ease of use, and quality. Before you make a purchase, you should consider include the weight, speed, drill chuck, rotation stop, impact rate, and individual impact strength of the hammer drill. The best hammer drill is one where the individual components work together in the best way possible.

The following criteria paint a picture of what you should be looking at when choosing a rotary hammer. However, make sure you don’t just focus on one or two aspects. The best hammer drill machine for your needs will depend on how well these factors interact with and complement each other.

Power: This is expressed in watts. In basic terms, the greater the watts, the greater the power. However, this is not necessarily true for the power of a hammer drill, because it also depends on how the tool was constructed, and the quality of the parts used. In any case, a higher max wattage means the drill can last longer without overheating. The lower limit for an electric hammer drill should be around 500-600 watts.

This applies mainly to corded devices. However, many DIY enthusiasts also enjoy using cordless hammer drills for everyday tasks. In this case, the power is measured in volts. Bosch, for example, has electric hammer machines with 12-volt and 18-volt battery systems .

Impact rate: This indicates the speed and rate of a hammer drill’s percussive hits, measured in beats per minute (bpm). A good bpm is normally around 4,000.

Individual impact strength: This parameter indicates the energy with which the hammer drill "strikes". It is measured in joules (J). An impact strength of 0.6J, for example, can penetrate concrete, but would not be sufficient for chiselling or drilling larger holes.

Tool holder: Most modern rotary hammers are equipped with the SDS chuck developed by Bosch. A Bosch SDS hammer drill not only guarantees optimum power transmission, it also enables drill accessories to be changed quickly and without additional tools .

In addition to these fundamentals, there are other factors that can improve the effectiveness of rotary hammers. These include whether the tool has the ability to reverse the rotation direction (for unscrewing screws, for instance), and whether it can utilise the Bosch Vario-Lock for more liberal chiselling applications (as the chisel must not rotate when in use). Also, you’ll want to consider whether to buy a corded hammer drill or not.

Some rotary hammer drills even have a 2-speed gearbox to provide optimum control over speed and torque. The Bosch Electronic Speed Control, an additional variable speed control system, is available for work on specific materials.

Rotary hammer drills and safety

A good DIYer should know how to be safe in their work. When working with powerful tools such as hammer drills, it goes without saying that you should pay critical attention to health and safety. Always remember the following rules:

Always wear safety goggles and ear protection, and wear gloves when chiselling.
Make sure you are securely positioned with sure footing (particularly on ladders or scaffolding).
Before using the tool, check that the chisel or drill bit is firmly secured in the receptacle.
Before changing accessories, disconnect the hammer drill from the mains electricity or remove the battery.

Hammer drills: frequently asked questions

Before you make a purchase, you’ll no doubt have a few questions about rotary hammers. Below you’ll find everything you need to know about hammer drill, so you can make a well-informed decision before buying the right tool for you.

When do you need a hammer drill?

A Bosch hammer drill machine is the “guy for the rough stuff” - it can drill into almost any hard material. Need to drill some holes in reinforced concrete? Got a need for cutting slots in cables? Got some tiles on a concrete wall that need shredding off? Then the hammer drill is the right tool for you. A hammer drill for concrete is like what butter is for bread: an obvious choice.

The hammer drill is generally a reliable partner when you need to do the tough work. Unfortunately, however, it is not suitable for precise drilling in softer materials.

Can you chisel with all hammer drills?

You can generally use all hammer drills to chisel off material such as tiles or plaster. However, smaller hammer drills have chiselling limitations due to their reduced power and performance. This means they are not suitable for harder materials or longer projects.

If you need to use the hammer drill for chiselling, make sure that you pick a device that has a switch to turn off the rotation. Then, instead of a drill bit, insert a chisel into the SDS socket of the hammer drill, and the tool essentially becomes an electric chisel.

Hammer drill vs impact driver: what’s the difference?

In addition to how they work, the two types of tools differ in what they are suitable for and how much physical effort you have to put in.

With a rotary hammer - as the name indicates - the drill bit rotates while a percussion mechanism provides a hammering effect. The percussion mechanism is coarser than that of an impact drill and smashes the material in a stroke-like movement. Although the impact frequency is lower than that of an impact drill, a rotary hammer’s force is much greater due to the stroke-like hammering method.

An impact drill also uses a percussion mechanism, but the energy is generated purely mechanically. Two sets of toothed gear discs interact with each other, creating a horizontal back-and-forth movement of the drill bit and chuck. Compared to the rotary hammer drill, the mechanical percussion mechanism of an impact drill is weaker but more precise. As such, it’s better suited to drilling holes in softer materials.

An impact drill’s mechanism only engages when you apply force with the drill against a material. The harder the material is, the more force you’ll need. With the rotary hammer , on the other hand, all you have to do is hold it in the right position, apply a little pressure and let the machine do the work.

Take a look at the Bosch website for numerous tutorial and explanation videos on the different types of hammer drills. Plus, we’ve got articles and guides to help you choose the best tool for the job .

How many watts should a hammer drill have?

Like horsepower for cars, watts are an indication of power for hammer drills. A 900-watt hammer drill is twice as powerful as a 450-watt model.

How many watts you need depends on various factors, such as the frequency you’ll use the tool. If you often drill through hard concrete or with large diameters, you should invest in a more powerful model.

What is measured by “joules” in hammer drills?

The joule measures the amount of energy in each drill impact. However, it is sometimes determined in different ways - check whether the manufacturer follows Procedure 05 of the EPTA (European Power Tool Association). This standardised measurement method allows you to directly compare the individual impact energy of different hammer drills.

What is a hammer drill used for?

A rotary hammer is designed for drilling holes in hard materials, such as concrete. A rotary hammer drill is an essential tool for building, remodelling or renovating your own home, as drilling into walls and ceilings is often required.

Additionally, rotary hammers that can switch between hammer and rotation modes can be used with a chisel attachment for chiselling and demolition work.

Relatively light work, such as installing a new house number on your stone wall, can be done with a rotary hammer drill. A pneumatic hammer drill is also ideal for chiselling slots in brick walls to insert electricity cables and water pipes, or for drilling plug socket holes.

Here’s a selection of what DIY projects you can use a hammer drill for:

Stripping and fixing damp walls.
Use a hammer drill to remove tile adhesive.
Laying electricity cables.
Installing a stretch ceiling .
Boring holes in concrete - use a concrete hammer drill.
Fixing objects, like floating shelves , to walls - although this may depend on the object and type of wall.