When drilling a hole...
If you need to drill a wall, whether in masonry (eg brick) or concrete, you can choose between two types of machines: percussion drill or drill hammer.
Both power tools use the rotation of the bit with impact to break up the material (eg concrete) however they use different internal mechanisms to cause the impact.
Figures 1 and 2 illustrate the differences between the two mechanisms:
- in the drill (Figure 1) there are two toothed discs that rotate together until the point where they “disengage” and cause a sudden descent on top of each other;
- in the drilling hammer (Figure 2), the impact is caused by a piston connected to a connecting rod-crank system. In this system, a piston is in a cylinder and displaces a column of air when it moves forward and it is this column of air that moves a body that causes the impact on the bit.
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| Figure 1 - Drill percussion mechanism |
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| Figure 2 - Drill hammer percussion mechanism] |
And what do these differences translate into practice?
The rotary hammer mechanism provides less wear on components, more impacts per minute, and higher impact energy compared to the hammer drill mechanism making it the tool of choice for professionals.
In practice, if we have few holes to drill (up to 10 mm pe diameter) then we can opt for a hammer drill. However, if you need to make dozens of holes and/or considerable diameters (up to 28 mm) then, without a doubt, you should opt for the drill hammer.
The types of drills used….
The differences between these two tools are not only in the mechanism that delivers the impact. We can also observe that the way we fix the drill in the bushing is done differently.
In drills, the chuck is tightened manually (with or without a wrench) in which normally 3 clamps 120º apart radially tighten the cylindrical drills.
In hammer drills, the chuck has a quick-fitting system called SDSPlus, which uses a ball that holds the drill through its own notch.
We can therefore assume that for drills we should use cylindrical drills and for drilling hammers SDS Plus drills as can be seen in figures 3 and 4.
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| Figure 3 – Chuck and cylindrical drill typical of a percussion drill |
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| Figure 4 - Bushing and SDS-Plus drill typical of a drilling hammer |
One of the outstanding functions that the drill usually has and the hammer drill does not, is the possibility of selecting the rotation speed as exemplified. This function is particularly useful e.g. for drilling ceramic tiles where you want a very low rotation speed and no impact.
A special feature of drill hammers is the chiseling option that allows small removal of materials with a pointer or chisel.
Both tools have the option to use or not use percussion (impact), reversible right / left rotation and allow variable speed. Then the models vary according to the hole capacity they allow.
In the most recent models of drilling hammers there is the option of replacing the quick chuck that allows the use of cylindrical drills as shown in figure 5. There are also chucks for cylindrical drills with SDS-Plus adapter that can be attached to any drilling hammer with the same system.
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| Drill Hammer BOSCH GBH 2-28 F |
Therefore, normally, drills are marketed for drilling metals, wood and ceramics and drill hammers essentially for concrete, masonry and stone.
The BOSCH GSB 13 RE impact drill and the BOSCH GBH 2-21 rotary hammer are the most basic models in the BOSCH professional range and offer a quality/price ratio that is much above average, making them the best sellers in their category in our store. .