Hammer drills (also known as impact drills or percussion drills) are incredibly versatile tools that are capable of performing many trying tasks. These tasks include a hammer drills ability to easily penetrate masonry, which comprises of materials such as bricks and concrete. This ability is the main difference between a hammer drill and a rotary drill or high torque drill.
Hammer drills are also extremely adept at boring various size holes through metal, wood and plastics.
The hammer function is the setting used on hammer drills to drill through masonry. This ‘hammer action’ enables the drill to produce rapid vibrations that chip away at masonry work whilst the chuck continues to rotate.
The ‘hammer action’ is produced by two metal plates connected to the drill’s drive shaft that have opposing raised edges. These plates connect when pressure is applied to the chuck, and as the chuck rotates, these plates rapidly move the drive shaft back and forth. Therefore, the faster the drill rotates, the faster this ‘hammer action’ is, and the faster it becomes to drill through masonry. The rating on hammer drills to indicate the maximum speed of this ‘hammer action’ is the blows per minute (bpm).
Hammer drills feature many different components, and having a sound understanding of these plays an important part in finding the best hammer drill for you. Knowledge of these parts also aids in the efficient and effective use of the tool.
The power source is the component that provides the tool with electricity. On hammer drills, this is done through a wired connection to a mains power supply. In Australia, hammer drills operate off mains power (240V) through a 10A socket.
Cordless hammer drills that are powered by a battery and a charger are also available and bear very similar features to those described below. They are generally not as powerful as their corded equivalents and require regular charging, but are usually considerably light in weight and have unmatched portability.
The switch allows the electricity from the power source to flow through the tool. All portable drills are activated by a trigger switch. When this trigger is pressed, the drill will begin to operate.
The most common type is the variable speed trigger. The further you depress this trigger, the faster the drill will rotate.
On some drills, a small dial in the middle of the trigger controls the variable speed. This construction allows for more accurate speed selections.
This button can be pushed while the trigger is depressed and the trigger will lock on to that set speed. To cease this function, simply pull the trigger.
Make sure this button has been released prior to disconnecting the tool. If not, the tool will begin to operate upon reconnection and may result in injury. For more safety recommendations, click here.
With a flick of this switch, the drilling direction changes to allow for forward and reverse motion (right and left motion respectively). This feature is found on all hammer drills, and can be very helpful if you need to remove screws, or if you need to release your drill bit after it has jammed in a hole.
If flicked between forward and reverse in a neutral position, it also locks the switch to prevent accidental operation of the tool.
You should never change the direction of drive whilst the tool is still operating, as it is highly likely you will damage the tool’s gears.
On hammer drills, the mode switch allows you to choose between normal drilling and hammer drilling (for masonry drilling). These symbols are illustrated and described below.
This mode disables allows for powerful rotary drilling and screw driving.
This mode engages a hammer drill's hammer action.
Hammer Drill Motors
Motors are the main component of all power tools, and are the component that converts the electricity into motion. The power that motors produce is measured in Watts (W). Motors used in portable electric drills are called AC motors (they are also known as universal or series motors).
Hammer drills vary greatly in size, and the input power of motors can range from 500W to 1200W.
Many manufacturers will state only the input power of the drill, as this is the larger and more impressive number. This value is actually just an indication of the demand a tool will place on a power outlet under normal operating conditions. The power output at the chuck, though, is significantly less than the input power. This is due to the efficiency of the drill’s internal components, and how power is transferred through the machine. Generally speaking, higher quality tools have greater efficiency and require less input power to produce the same power output. Therefore, although it is uncommon for most manufacturers to include a power output value, it is a much better way of comparing tools and finding the best hammer drill.
Most professional quality tools will have a round port on either side of their housing. These ports give simple access (with a slotted screwdriver) to the most frequently wearing component of any tool – it’s brushes.
Also known as a gearbox, transmissions dictate the speed range (revolutions per minute, or rpm) that a drill can operate at, and the corresponding torque (or turning force) that it can produce.
Transmissions can contain single or multiple gears that are driven by the motor. If a small gear is used in the transmission, then rotary speed will be high but torque will be quite low. If a large gear is used, then rotary speed will be quite low, but torque will be high.
Electric drill accessories come in many different sizes, and all have a recommended speed that they have been designed to operate at. To accommodate these requirements, you must have a drill that has both enough torque and enough speed to handle the accessory.
To acknowledge this fact, manufacturers will state the maximum drilling capacities that a drill is capable of drilling into various materials. These materials are wood, metal, and masonry.
The optimum drilling capacities of drills are where they will deliver their best performance. If you halve the drill’s maximum drilling capacity, it will give you the optimum drilling size, and is the size of hole you should be most frequently drilling with that drill.
Hammer drills can be broken up into two main categories; hammer drills with a single gear, and those with two gears.
Single-Speed Hammer Drills
These hammer drills have only a single gear and are the cheapest and most common available in tool shops. They usually weigh between 1.5kg and 2kg.
They can usually attain maximum speeds of about 3,000rpm (very similar to a rotary drill). The speed is still dictated by a variable speed trigger of course, and this allows the drill to perform a multitude of tasks. When the drill is switched to hammer mode, these drills typically produce about 45,000bpm.
On average, single-speed hammer drills are able to drill a 15mm hole into masonry, a 13mm hole through metal, and a 30mm hole into wood.
These maximum drilling sizes depend on the specific model of the drill, and it is recommended that you consult these specifics before making a purchase.
Two-Speed Hammer Drills
These drills are titled ‘two-speed’ because of their two-geared transmission. This style of transmission gives these drills a huge advantage over single speed hammer drills in nearly every aspect. They are generally much heavier than their counterpart however, weighing in between 2 and 3kgs. Two-speed hammer drills can be distinguished by a numbered gear switch or dial located on the top or side of the drill.
When in first gear (much like a car), these drills turn at a slow speed but produce a very high amount of torque (turning force). This torque, combined with the hammer drill’s powerful motor, enables them to perform applications otherwise only recommended for high torque drills.
When the second gear is selected, revolutions per minute (rpm) pick up but torque is reduced. This is a perfect setting for smaller holes in wood, and metal. For average size masonry holes, this is also the ideal setting, as blows per minute (bpm) are increased dramatically on this higher setting. The varying speeds for each gear are of course dictated by how far the variable speed trigger is depressed.
For a typical two-speed hammer drill, maximum speeds for both gears are 0-1,200/0-3,000rpm (first and second gear respectively). Consequently, 0-20,000/0-55,000bpm ranges are customary.
Capacities vary amongst different models, but the best hammer drills with two-speeds should be able to drill a 20mm hole into masonry, a 15mm hole in metal, and a 40mm in wood.
These maximum drilling sizes depend on the specific model of the drill, and it is recommended that you consult these specifics before making a purchase.
The more powerful models of hammer drills may also come with torque limiters or clutches, which reduces potential damage to the user and the drill if the drill bit jams during use.
Hammer Drill Chucks
The chuck is the part of the drill that grips drilling accessories. The transmission powers the drive shaft and on the end of this shaft is the chuck. On hammer drills, there are two types of chucks – keyed and keyless.
Keyed chucks have a solid metal construction – which makes them very durable through excessive vibrations and dust – and are operated by a chuck key. When fitted to the chuck, the chuck key fits into the gear notches of the chuck. As you turn it, it either loosens or tightens the chuck (depending on the turning direction).
It is a good idea to use the chuck key on all three notches of the chuck to ensure each jaw is securely tightened.
Keyless chucks are much faster to use, and can be operated completely by hand. Depending on the quality and purpose of the drill, these chucks can be plastic or metal, or a combination of the two, and usually have a front and rear sleeve. To loosen/tighten the chuck manually, place one hand on the rear sleeve of the chuck and turn the front sleeve right/left. To do this with the aid of the drill, hold the front sleeve of the chuck while you apply some reverse/forward acceleration to the drill.
Keyless chucks on the best hammer drills will also have a locking and/or ratcheting feature when you tighten them so the chuck will never come loose during operation.
Due to their heavy-duty nature, it is common (and recommended) for these drills to have either a 13mm (1/2”) keyed or metal keyless chuck.
Generally speaking, most chucks on drills of this size have the capacity to hold down to a 1.5mm (1/16”) drill bit.
The housing of a drill is the casing that protects the internal components.
Hammer drills will have either a clamshell housing, or a jampot housing.
A clamshell housing is where the housing is manufactured in two plastic halves, and where these halves are fixed together around the internal components.
A jampot housing is where the internal components of the drill are inserted into the housing and then a lid (usually an alloy casing) is screwed down to seal it. This durable style of housing is generally used only on the best hammer drills, and is much more effective at keeping the internal components aligned and the power tool structurally sound.
Most larger hammer drills have a very robust and durable aluminium gear housing (as part of a jampot housing) that enables much better gearbox heat dispersion and therefore a potentially longer lasting drill.
These drills may also have anti-vibration technology built into the housing, which helps to prevent frequent users from acquiring severe conditions such as Hand Arm Vibration Syndrome (HAVS).
Others may also have spirit level vials built into the top and/or rear of their housings that allow you to ensure you are drilling at a 90° angle to the material.
Handle Of A Hammer Drill
The handle is the component of the drill that you hold with your dominant hand and is what you use to apply pressure to the drill.
On hammer drills, the handle is called a pistol-grip handle. Toward the top of the handle on some of the best hammer drills there will be a finger mould for your thumb and index finger. This feature allows you to apply forward pressure in a more efficient manner, by pushing in line with the drive shaft and chuck. The pistol grip handle is commonly partially covered by rubber for user-comfort too.
This handle is designed to stop rotation and to provide stability for the user. It is secured just behind the chuck and can be positioned at various angles to the body. The angle is generally changed by unscrewing the handle, moving it, and screwing it back up.
The depth stop is a small plastic or metal rod that sits in the side handle, and can be set to certain lengths in front of the drill to monitor the depth of holes.
This is especially useful if you are drilling holes where the drill cannot go through the material or if you need to drill holes of a certain depth.
For a comprehensive guide to the best hammer drill accessories, please see our separate drilling accessories section.
When purchasing the best hammer drill for you, decide what features are most important to you (from the features above) and make sure these are included in your final purchase. The main considerations you should make include how much power you require, the size and weight of the tool, whether you need it to be cordless, and how often you will be using it.
A hammer drill should be of solid construction, comfortable to use, and should be able to accomplish the vast majority of drilling jobs that need to be done.
Manufacturers will either direct their products at the DIY or professional market. DIY tools are designed for home use and generally include plenty of features for a very modest price. They also tend to have very generous warranty periods, including replacement warranties. Professional tools are designed for commercial use and are built for durability, performance, and reliability. Their warranty periods tend to be much shorter than DIY tools, and are exclusively repair warranties. The main advantage of these tools is that they should well outlive their warranty period, and if they require repair and maintenance spare parts are readily available.
The price of any tool will depend on the quality, capabilities, and features of the model. Bear in mind that at least one of these three elements is commonly sacrificed by manufacturers to reduce the tool’s price and increase its sales. After all, price is the most important factor for consumers.
Hammer drills can cost anywhere from $30 to $500.
It is important to bear in mind that the entire cost of any power tool is not just it’s initial purchase cost. Added costs can include accessories for the tool to function, maintenance, downtime, and replacement costs. Buying according to your requirements will help to keep these costs to a minimum.
The following tips will help to preserve the life of your hammer drill, increase your efficiency, and most importantly, keep you safe.
Personal protective equipment (PPE) must always be worn when operating power tools. For more information on PPE and power tool safety, click here.
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