What kind of hammer drill do you need?

The main task of a drill is drilling. You can probably imagine how it works: the drill bit clamped in the chuck rotates, removing material and creating a hole the diameter of the bit. This is the procedure for drilling into soft materials. However, if you need to drill a hole into construction materials such as brick, concrete, or stone, you need a drill with an impact mechanism. Hard material must first be broken up and only then drilled away.

According to the principle of operation, we distinguish between 2 types of impact mechanisms:

• Mechanical impact
• Electropneumatic impact

Let's explain the principle of operation for both types in more detail.

Mechanical impact

Mechanical impact works by the chuck moving forward and backward together with the drill bit thanks to gears. As they rotate, these gears skip over each other, creating the movement we call "impact" or "hammer action" (positions 1, 2, 3 in Fig. 1).

Fig. 1 Principle of operation of mechanical impact

This type of impact is not suitable for drilling into concrete, but rather into brick or aerated concrete—soft construction materials. During drilling, it is felt as slight vibrations of the tool. To achieve the desired effect, you must press on the drill with a force of 5-10 kilograms.

This type of impact is used in classic electromechanical drills or in cordless screwdrivers. They are commonly called hammer drills or simply drills (Fig. 2).

Fig. 2 Drilling with mechanical impact

Electropneumatic impact

The electropneumatic impact has more components and a more complex mechanism.

It consists of a tool holder (1), a striker (2), a free piston (3), a driving piston (4), and a crank mechanism (5) as shown in Fig. 3. The crank mechanism moves the piston, which repeatedly compresses the air in front of it, transferring blows to the striker, then to the impact bolt, and directly to the drill bit. Through this regular striking, the drill bit acts like a chisel that breaks the material, and the rotating movement through the drill bit's flute carries the drilled material out of the hole.

Fig. 3 Principle of operation of electropneumatic impact

Fig. 4 Drilling into concrete with an electropneumatic hammer

Its efficiency is significantly higher than that of mechanical impact. The energy of an electropneumatic impact or blow is given in Joules.

Drills with SDS-plus tool holders have an impact energy of 2-5 J and a weight of 3-5 kg.

Drills with SDS-max tool holders have an impact energy of 6-20 J and a weight of 6-12 kg.

Based on these data, we can choose the right hammer drill for our work. This type of "drill" is professionally called an electropneumatic hammer or rotary hammer (Fig. 4).

Use of hammer tools

An electromechanical drill is best used with the impact turned off, especially at home for drilling into wood and metal, or with the impact on for soft construction materials.

The electropneumatic hammer is used for drilling into concrete and stone. This determines its use for commercial construction work, but of course also in the household when drilling into hard construction materials.

How to drill properly

Mechanical impact works with a much higher number of blows (several tens of thousands) than electropneumatic impact (several thousand), but with much lower blow energy.

When drilling with mechanical impact, we cannot influence the impact energy, so the rule is: the harder you press on the tool, the faster you will drill.

However, when drilling with electropneumatic impact, by pressing on the tool, you reduce the piston's travel and thus the impact energy. Drilling will therefore be slower. For optimal performance, it is recommended not to press on the hammer at all—let it work with its own weight, which also extends the life of the components.

Sources:
HERMAN internal technical and training materials
https://cs.wikipedia.org/wiki/Elektropneumatick%C3%A9_kladivo
https://cs.wikipedia.org/wiki/Vrtac%C3%AD_kladivo

Karol Bryndzák

I have been selling tools at Herman for nine years. I personally tried all the products during the renovation of my parents' house, which helped me to better understand their functionality and advantages. I am glad that I can pass on this practical knowledge to our customers in selling them our products. I am interested in news in the world of tools, and I like to follow the development of new technologies that can make our lives easier. I spend my free time working around my family home, with my family and music.