When drilling holes in concrete and other hard materials, a task that requires robust mechanisms based on firing actions, a rotary hammer, rotary hammer or rotary hammer is the perfect option for a simple drill that is not powerful enough to do this. job.
The structure of a rotary hammer It includes basic elements common to other similar tools, such as a motor (powered by cable, battery or pneumatic system), transmission gears, a percussion mechanism and a chuck or tool holder to which various accessories are attached, consisting mainly of bits and chisels. All these elements are inside a housing, provided with special handles and control buttons.
The principle of operation of the rotary hammer It is based on destroying the structure of the processed material as a result of translational or rotating movements of the accessory. This means that a series of mechanisms, properties and parameters are combined in a rotary hammer that we must carefully consider when we are going to acquire a tool of these characteristics.
In this article, therefore, we are going to review some of those considerations to help the reader select the rotary hammer that best suits your needs.
The first thing we must take into account is related to the choice of the type of tool itself. This is because of the many tools we have for drilling holes, there are only two when it comes to concrete: the hammer drill and the rotary hammer. Therefore, we must first check if what our work requires is actually a rotary hammer, or instead we can use a hammer drill, which is simpler and cheaper.
1) Rotary hammer or hammer drill?
A hammer drill is an improved version of the standard drill and is generally used in relatively softer materials, such as lightweight concrete or masonry, or where drilling requires holes up to 10mm in diameter. The rotary hammer It features a rotating part to move the tool in a more circular motion, resulting in more powerful drilling of larger holes in a masonry or concrete surface, and is therefore the right tool for use in more concrete. hard or for holes larger than 10mm.
As he hammer drill such as the rotary hammer hit your bit as it rotates and pulverizes the concrete, but the tapping mechanism works differently on the two tools.
The hammer drill uses two fluted discs that rotate in contact with each other. When the opposing splines strike each other, the impacts are transmitted to the drill bit and cause the characteristic hammering sound. For heavier jobs, it is much more efficient to use a rotary hammer than a hammer drill. The rotary hammer uses a piston that repeatedly compresses the air above it and causes strong movements that are transmitted directly to the bit, allowing us to do the same jobs in less time and less effort.
In the following table we detail a quick comparison between a rotary hammer and a hammer drill to better understand their differences and applications.
Once we decide that what we need is a rotary hammer, let’s examine the details of this tool that we need to consider.
2) Type of rotary hammer: horizontal or vertical?
Depending on the location of the motor, we can choose between horizontal rotary hammers (when the motor is parallel to the impact axis) or vertical (when the motor is perpendicular to the impact axis).
Horizontals are preferred for working in narrow grooves as they are longer and narrower. Most home rotary hammers are horizontal type. For their part, vertical rotary hammers (or “L”) have advantages in terms of power and engine cooling capacity, which is why most professional rotary hammers are vertical.
3) Electric power
This parameter, measured in watts, is very important in determining the capabilities of our tool. In the trade we will find rotary hammers with powers ranging from 450 to 2000 W. Although there is no clear division into categories, we can establish that powers of up to 900 W are the most suitable for rotary hammers intended for home use, while over 900 W are preferred for rotary hammers for professional use.
This means that if, for example, we need to drill a thick wall, it is advisable to choose a powerful rotary hammer, of at least 1500 W. On the other hand, if professional repairs are not part of our usual activity, we can opt for a good 750 tool. -900 W. DIY enthusiasts or hobbyists who might use a rotary hammer a few times a year will find a 550-600 watt power tool ideal.
4) Impact power
This other parameter, measured in joules, shows the energy that the rotary hammer possesses for its interaction with the workpiece. The efficiency and speed of the tool depend on this magnitude, which is directly proportional to the electrical power.
For example, some manufacturers offer 750 W and 2.8 J models (electrical power and impact power, respectively) that can drill holes in concrete with a diameter of 26 mm or more.
Other more robust models have an electrical power of 1500 W and an impact energy of 20 J, with the capacity to drill holes up to 52 mm in diameter in concrete.
However, if we do not carry out this type of heavy work, we can choose a model perfectly adapted for daily use with impact powers that vary between 2.6 and 4.5 J. This option is especially suitable for installers of ventilation systems and air conditioners, electricians, plumbers, siding and carpet installers, etc.
5) Rotation speed and impact frequency
These parameters indicate the amount of rotary and translational movements of the rotary hammer per unit of time.
The impact frequency ranges from 2,150 to 5,800 strokes per minute. In turn, the rotational speeds vary between 230 and 2300 rpm. Tools for domestic or light applications have higher rotational speeds (1500 to 2000 rpm) while professional tools have lower speeds (230 to 450 rpm).
If we are looking for a rotary hammer for light use or for DIY we can recommend a model with a rotation speed of 1000-1500 rpm and an impact frequency of 4000-4500 strokes per minute.
6) Mandrels and inserts
The chuck is a device for attaching work accessories, such as drill bits, chisels or others. Its size depends on the type of accessory it can accommodate, is related to the power of the rotary hammer and is generally associated with the type of drive.
In the 1970s, Bosch launched the SDS socket, which provided a more efficient system for producing a hammer blow at the end of a rotating bit, without impacting the chuck. Later the SDS-plus insert appeared, which had an improvement in the stem with respect to the SDS model and worked interchangeably with it, but with a better connection. Today, the SDS-plus insert is the most common in the trade.
However, as the need for heavy-duty drills in concrete and masonry arose, the United States introduced the spline socket, while in Europe the SDS-max model appeared, intended to replace the spline for drills. larger, with the same strength and capacity, but with better connectivity similar to the smaller SDS bits. However, this replacement never took place in a decisive way, which is why in the United States it is still very common to commercialize rotary hammers with grooved insertion.
The figure below shows the profiles and symbols for each type of socket currently in use.
In order to choose the right chuck / socket model for our needs, let’s remember the following:
- SDS and SDS-plus socket: It is 10 mm in diameter and is the one presented by lightweight rotary hammers for semi-professional or home use. Typically used with 5/32 ”to 1-1 / 8” carbide bits and carbide core bits up to 4 ”for thin walls, as well as small chisels. If we buy an SDS or SDS-plus rotary hammer, we can use SDS or SDS-plus accessories interchangeably.
- SDS-max socket: professional rotary hammers come with SDS-max chucks, which are 19mm in diameter and are generally used with 1/2 “to 2” carbide bits and carbide core bits up to 4 “for thick walls or up to 6 ”For thin walls. In addition, they can receive shovel, cold cut, hammer, excavation chisels, etc. If we acquire a SDS rotary hammer o SDS-plus we must bear in mind that we will NOT be able to use SDS-max accessories, since they are incompatible with that type of fitting.
7) Anti-vibration system
If we are going to use our professional rotary hammer in repeated demolition or drilling work on very hard surfaces, it is clear that we will have to address the problem of vibrations associated with this activity, capable of affecting the health of the worker.
To this end, some manufacturers incorporate an anti-vibration system in some models of their line of robust rotary hammers. These systems are based on dynamic damping to dramatically reduce rotational vibration by almost 50% compared to similar products while increasing impact power by up to 75%. Among the advantages of anti-vibration systems we can point out the following:
- Protect the worker from hand and arm vibration syndrome (HAVS)
- They contribute to the health and fitness of the worker
- Reduce worker fatigue, allowing higher productivity
- Facilitate tool control to provide a better finish
In addition to those listed, each manufacturer offers other functions in their rotary hammers that are specific to each brand and that we can consult with a salesperson or specialized representative. Consideration of as many features as possible will allow us to make a smart purchase that is perfectly adapted to the intended use.