Crowns for concrete for a hammer drill: sizes, types and rules of use

Often, when re-planning, overhauling, changing the interior, the question arises, how to create a hole in concrete or brick walls for a switch, an electrical outlet or conductive pipes? Ordinary drills for wood or metal in such situations, of course, are not suitable: they will instantly lose their properties. Specialized fixtures are required, including concrete crowns of various sizes.

As a result, the availability of drilling tools ready to drill holes in concrete structures is extremely important for any type of construction (residential, public, industrial). A bit for concrete is one of the types of drilling equipment, through which holes are drilled in the supporting and enclosing structures of buildings and structures made of concrete. This procedure is necessary when performing the following work:

• laying of networks of engineering and technical support of various directions: sewerage and water supply, electric networks and communication lines, automation and fire extinguishing systems;
• installation of technological and electrical equipment;
• installation of anchors and other fasteners;
• installation of components of supporting and enclosing structures for a wide variety of purposes.

The crowns are produced only from hard alloys of metallic materials, which make the product strong, durable and effective. It is not uncommon for beginners to wonder for what purpose a crown has a centering drill? Precise holes can be made with this drill. Its absence can lead to vibrations during drilling - the hole will be deformed, distorted and uneven. Bits are classified according to shank design. They are available in the following types.

• SDS-plus - models that are installed in household rotary hammers.

• SDS-max - used exclusively in professional rotary hammers. The shank diameter is 20 millimeters.

• Hex Shank Drills - This type of drill is used to drill large holes with an electric drill.

Crowns differ between themselves in the material from which the cutting area (teeth) is made. There are 3 product options.

• Victory - for the manufacture of teeth for the crown, an alloy of cobalt and tungsten is used in a ratio of 8% and 92%. The characteristic properties of these nozzles are resistance to high temperatures and long-term loads. They are used for reinforced concrete or brick.

• Carbide - this type of product is considered budgetary and is intended solely for making holes in concrete foundations. Impact with iron will damage the teeth of the carbide crowns.

Diamonds are among the most expensive, but also effective. Diamond drilling tools have a number of positive qualities: they are not afraid of meeting with metal.That is why it is possible to make a hole in reinforced concrete only with tools of this type. There are many modifications on sale with various diameters. In addition to the especially popular 68 mm concrete crown, devices for concrete 100 mm, 110 mm, 120 mm, 130 mm and 150 mm are also in demand. Equipment with such a large diameter is used for drilling holes in reinforced concrete or brick walls for pipes. The quality of the resulting hole is very high: there are practically no chips, cracks or other surface flaws.

Nozzles that have holes on the side walls of the bowl are dry. Bowls of a closed type are considered wet, which must be wetted with water during drilling. It is possible to wet both samples of nozzles with water, since this will not only increase the service life of the devices, but also reduce the accumulation of dust formed during the drilling process.

Based on the drilling technology, the nozzles are additionally divided into non-impact and impact bits. The first option is suitable only for functioning in the drilling mode and is often used for electric drills. Impact devices can be operated using the function of a jackhammer on the rock drill.

For the correct choice of a crown that is appropriate in size, it is necessary to know the diameter of the hole to be created for an electrical outlet or other component - for example, for the diameter of pipes or the coverage of a wiring line when installing electrical communications. When buying a crown at a retail outlet, you need to find out from the sales assistant its technical parameters, which are available in the attached documents or on the marking. Crowns can be realized both by individual products and by special sets of several units of different sizes.

The main component of switches or installation boxes for sockets is located with a standard outer diameter - 68 millimeters (with an inner diameter of 60 millimeters), therefore, concrete crowns for boxes for 68 millimeter sockets are the most demanded devices. Less nozzles are used at 70 and 75 millimeters. For laying communication lines, nozzles with a diameter of 300 millimeters are especially common.

The set of concrete nozzles for boxes for sockets also includes a centering drill, the function of which is to concentrate the crown in the center of the hole being created, preventing vibration in the working material. The centering drill needs to be changed frequently as it dulls rapidly. The crown is designed to penetrate up to 1.5 meters into the material.

If the shank of the selected crown matches the clamping device of the rotary hammer, it simply needs to be positioned and secured in the working position, no adapters are needed. You can start drilling the concrete at the mark.

The nozzle can be equipped with a center drill or not. If there is one, then the point is placed at right angles to the concrete plane in the zone where the middle of the hole will be located. If the structure of the cup does not provide for such a drill, then the circle of the incisal edge is pressed against the concrete. Begin drilling without effort - the cutting edge must select a shallow tunnel and straighten its direction. When it can be seen that the nozzle is properly positioned, the tool is pushed forward with pressure.

It is not necessary to remove the drill until it has drilled the concrete to the required depth or the bottom of the crown rests against the wall. From the holes that are not made through, a roll of cut concrete is picked out with a lance.For gear nozzles with carbide solders, the main thing is to correctly determine the order of operation of the hammer drill. Excessive heating of the edge should not be allowed, therefore, after one or two holes, it is necessary to allow the device to cool down.

If it is necessary to prolong the service life of the nozzle on reinforced concrete, it is required to use water spraying, which cools the cutting part. This is especially true for fixtures with soldered edges, as they will fall off when heated too much. Such crowns are practiced for more sophisticated fittings than a manual hammer drill. It is fixed on reinforced concrete, and the operator only has to feed the drill, making the hole deeper.

When choosing a nozzle for concrete, it is necessary to take into account 2 important conditions: what is the concrete structure made of (concrete grade in terms of strength and parameters of reinforced concrete reinforcement), and with what equipment the crown will be used. Despite the fact that the lion's share of bits are compatible with various types of electric drills and hammer drills, it is impossible to say that every bit will fit every tool.

This comes primarily from the model of the hammer drill chuck - SDS-plus (they are equipped with light perforators weighing up to 5 kilograms) or SDS-max (it is put on more powerful and heavier devices). The bit must be with the correct shank. There are adapters that allow you to put one type of crown on a perforator with a different type of chuck, it is only advisable to choose a bit that exactly matches the tool.

For more on concrete crowns, see the video below.