Today, there is no need to use nails to hang a picture, shelf, cabinet or other piece of furniture and decor. Firstly, it is inconvenient, and secondly, it is unreliable. Any fasteners must be reliable, it is better to choose dowels that are installed in a pre-drilled hole. The reliability of such an attachment directly depends on the correctly selected drill, the smaller the difference between the diameters of the hole and the rod, the stronger it will be installed. How to choose a drill for a dowel, let's figure it out further.
Basic principles of selection
The correct choice of a drill for a dowel should be based on the following:
- When calculating which hole to drill for the dowel, it is worth considering the type of wall into which the rod is installed, and what it is covered with.
- The weight of the furniture to be attached and the maximum possible loads.
Taking into account the above parameters, you can correctly select the appropriate tool. To make it easier, you need to take into account the factory size of the drill and fastener, as well as the tensile strength of the dowel. The tool has a marking, focusing on which it is easy to choose the desired model.
If the wall material is very strong, such as concrete, two drill types and different drill modes should be selected. First you need to take a drill several sizes smaller than the dowels, switch the drill to percussion mode and make the necessary hole. Then, using a drill of the same size with the fasteners, in the usual mode, bring the hole to the required parameters.
With the help of such manipulations, you can carry out work faster, not overload the drill, get a hole in an ideal shape and preserve the integrity of the wall and its coating. The rod in the hole should not scroll and move freely in it. Instead of a drill, it is better to choose a rotary hammer, since it is more powerful and productive.
If the wall material is loose, it is better that the drill size is several sizes smaller than the rod (for example, for dowel 8, drill size 6 or 7). This will allow the fasteners to fit tightly, even in the event of excessive destruction of the wall structure.
When choosing the type of drill, you should pay attention to the victorious ones, given their high strength and durability.
The length of the hole should be several millimeters longer than the dowel. This is necessary in order for it to sit tightly in the niche along its entire length, since dust can accumulate in the hole.
Fastening light objects
Fastening shelves, paintings and other light items does not require special preparation and the presence of a powerful tool. You just need to have a power tool, a simple dowel and a suitable drill for the dowel. This type of fastener is great for concrete and brick walls. It can also be installed in the ceiling, for which you need to make a hole for the dowel 6. For walls, fasteners of 4 sizes are suitable. For this type of wall, a victory sting is best suited. In most cases, two mounting points will be sufficient.
Fastening products with an average weight
If the weight of the installed decorative element exceeds 5 kg, more reliable fasteners are needed. A dowel with a diameter of 8 mm is suitable and, accordingly, the diameter of the drill is also 8 mm. A hole length of 6 cm is quite enough when working with ordinary walls, when working with loose material or a ceiling, the depth is increased to 8.
If the weight of the object approaches 10 kg, for reliability it is worth installing 4 fasteners, since 2 may not withstand. It is better to use a puncher as a tool.
Securing heavy objects
Heavy furniture or household appliances that are mounted on the wall are physically demanding. Even if the fasteners look reliable at first, they can fail over time. Installation of heavy objects should be carried out only on walls made of durable materials, concrete or brick. Loose material can be shattered by heavy weight. The normal diameter of the fastener is 10 mm, and the hole depth is more than 6 cm, you need to rely on these indicators to determine the diameter of the drill. For reliability, the number of mounting points is recommended at least 6. Choosing which drill to drill, you can safely choose the victorious ones.
In order for the attached structure to support about 100kg, it is better to use.
They are more reliable even considering their smaller size. Make a hole up to 6 cm deep and install the selected bolt.
There are 3 types:
- A bolt with an outer nut that can be tightened with a regular wrench.
- Self-locking nut that can be tightened with a screwdriver.
- Double-expansion anchors, which are used to fasten the most massive furniture.
Fastening to an unreliable surface
Modern homes have many surfaces made from materials that are not very durable. These include drywall, old brick, wooden planks or boards made of pressed sawdust. When working with them, it is better to use nylon fasteners with a diameter of more than 10 mm, the installation depth should not be less than 6 cm.
The drilling process must be shock-free, as excessive stress can damage the surface. Using the impact mode may not leave visible damage, but the internal structure of the wall may suffer. If the drill diameter is too large, the fasteners will move freely in the hole, gradually increasing its diameter, especially if the work was carried out with aerated concrete.
For plasterboard walls it is not necessary to use a drill of a smaller diameter, the main thing is not to put pressure on the drill and do not use the percussion mode. Drywall is a very delicate material, even a small load can lead to the destruction of a section of the wall. The hole should be drilled with light force to match the size of the plastic dowel with a self-tapping screw.
It should be understood that it is not necessary to attach heavy structures to such surfaces, even if the material initially copes with the load, over time, under heavy weight, collapse may occur.
If you take into account the material from which the wall is made, choose the right dowel and drill for it, and also having a quality tool in your hands, you can make a high-quality installation, and not worry about the safety of your furniture or household appliances... Observing the recommendations, even an inexperienced master will cope with such an installation.
A dowel is a fastener element, which is a kind of fixation for a component that performs the main function of fastening. Usually, a screw or self-tapping screw is inserted into a dowel, which has a cylindrical or other (volumetric) shape and a groove, along the central axis. For example, the use of dowels is required when there is a high probability of damage to the product or the formation of a fragile connection if the main fastener is directly inserted.
The name "dowel" has German roots, it translates as a dowel, an insert tenon or a dowel. Nowadays, a suitable dowel is not difficult to obtain due to the wide range of products. How to make a choice among numerous models and manufacturers, in which even professionals sometimes get lost?
When looking for a suitable dowel, you need to be guided by the following criteria:
1. What product do you need to attach?
2. On what basis will the fastening be made?
3. Time spent on work. It is necessary to carry out the fixation urgently or extremely reliably, but spending more time.
Fixed item and base
Mounting materials can be divided into 4 types:
1. Corpulent (no voids): concrete, brick.
2. Hollow blocks of expanded clay and concrete, slotted bricks.
3. Solid materials with pores (aerated concrete).
4. Drywall and gypsum fiber sheet.
Understanding the features of the fixed product makes it possible to determine two problems: the need to preserve the aesthetics of the appearance and the required load on the fastening element.
The object is fastened using a dowel or a spacer. Experts often take these two concepts as synonyms or different types dowels. Sometimes spacers are called what is inserted into the dowel (hooks, nails, screws, screws). All fastener parts are often sold together for ease of use.
Fragile materials cannot withstand the spacers that are formed as a result of the insertion of rigid elements into the dowel. The impact of the friction force does not allow the dowel to come out of the hole, but when the fastening zone is destroyed, it leads to a weakening of the fixation. Porous materials such as aerated concrete and aerated concrete are destroyed by the action of the spacer. Fastening critical structures, in fragile materials, it is better to carry out on a chemical adhesive solution in combination with an anchor element, which can be a threaded stud or a metal hook.
Fixing on dowels is a well-known method of fastening structures to each other. Dowels are used when the end of the fastening component (self-tapping screw, rod, screw) is not accessible for holding installation works... Often, for work at home, instead of dowels, wooden sleeves are used to secure the object to concrete or brick wall, there may be problems with plaster material. Holes are drilled into which the rod is hammered, then the product is installed on a self-tapping screw.
How to determine the material of the walls
Home owners usually know what the walls of their home are made of. The choice of the type of dowel depends on this. In the absence of information, it is necessary to drill a layer at a low speed. finishing material... For this, a winder drill is used. An indicator of the softness or hardness of a material is the effort required to drill. By flying away particles, you can determine what the walls are made of:
1. Concrete: light gray loose powder.
2. Drywall: particles stick to the drill, fine-grained white.
3. Foam concrete: large white particles, fragile when crushed.
4. Gypsum fiber sheet: gray dust sticking to the drill.
5. Brick: red flour, a drill that fails periodically is a sign of hollowness.
6. Sand-lime brick: white powder like sand.
Mounting
Dowels are chosen not only based on the supporting material, but also depending on the required installation speed. There are special dowels that allow you to create an attachment in a matter of minutes. For example, a dowel-nail, the installation of which is carried out by blowing a hammer.
On this figure shows the stages of installing the dowel
1. Drilling a hole
2. Cleaning (blowing) the hole
3. Installation of a dowel with a baited self-tapping screw
4. Twisting
5. Finished attachment point
Standard types of dowels
For use in each specific type of base material, it is necessary to select specific types of dowels. Most often, city houses are made of solid materials. For installation in them, a standard expansion dowel is suitable, which has a expansion screw or other expansion element in the kit. The latter act as spacers when screwed into the expanding cap.
The butterfly-shaped resin dowel is suitable for fixing lightweight structures to drywall. A secure fit is formed as a result of the opening of the rear part from the back of the material.
Universal dowels are fixed in any base material, depending on its type. In conditions of emptiness, the opening of the cap occurs like a butterfly, in full-bodied structures - spacers. The universal dowel withstands a lower load than the conventional (spacer) plug. 
There are many types of dowels. The choice of specific shapes depends to a large extent on the material of the item to be fixed and the base on which the fixation is made. In second place are the factors of the required speed of installation and operating conditions.
Examples of using dowels for various designs
Drywall or gypsum fiber - modern materials for wall decoration... To fix the elements on it, use butterfly dowels or specialized fasteners made of MOLLY metal. The latter, during installation, require the use of special pliers, as a result of which a quick opening (spacer) of the dowel inserted into the wall is achieved. It is also possible to fasten the elements with a screwdriver, but there is a high probability of the dowel turning in the hole, despite its teeth.
There are special dowels for foam and aerated concrete with an extended spacer zone in order to reduce the pressure on fragile material. Often, products for fragile materials have a special geometric shape. A long spacer area is typical for frame fasteners. This feature allows you to use these dowels for fixing frames on foam concrete.
For work with hollow bases, spring dowels or umbrella dowels are used. Sometimes a situation arises when voids are found after drilling. You can save the situation here with the help of such dowels.
This figure shows an example of the operation of a universal dowel in a hollow base (in this case, in a hollow brick)
In the void, part of the dowel folds into a knot that does not allow it to fall out of the structure
Fastening a door or window profile to a concrete wall
The frames are fastened using dowels that go through. The specific choice depends on the basis. If it is solid concrete, then ordinary dowels with a spacer zone are used. The dowel diameter is selected depending on the required load holding. When planning a light load, a 10 mm dowel-nail is suitable. There are specialized frame dowels for high loads. V modern world there are special screws that do not require dowels. The elements are specially designed for concrete.
Fixing thermal insulation material to a brick wall
The classic choice here are disc dowels, but the preference also depends on the type of insulating material, which are fixed on the base in two ways: hinged (ventilated) facades or the use of a thin coating of plaster. If the installation uses wet-facade technology, then a dowel with a metal rod covered with thermal protection is required. For the hinged method, products with plastic or metal rods are suitable. Without dowels, it will not be possible to fasten products to brick or concrete surfaces. The exception is wood, which does not require the use of spacers.
There are two main ways of fixing the dowels: expansion (for monolithic bases) and anchor (in the case of structures with void zones). There are universal types that can be fixed in two ways.
What you need to know about choosing a dowel
For each design, certain categories of dowels are suitable. Specific varieties always create a more reliable, high-load connection than generic types.
After determining the category of fasteners, it is necessary to resolve the issue with its size. Before work, you should choose a drill identical to the diameter of the dowel. The number indicated on the product indicates the dimension, for example, S6, which means 6 mm in diameter.
Construction and repair work and dowel selection
Do you need to hang a shelf, for example, for books or other things, while the base is made of foam concrete? The load on the product should be assessed, since books or flower pots add significantly to the weight of the structure.
The foam concrete base is not strong, and the attachment of weights to it requires knowledge of the nuances. There is a specific type of dowel (for aerated concrete blocks, foam concrete), which will help to cope even with a low-quality category of foam concrete. In the case of more durable base types, frame types with an oversized spacer section are suitable.
In the process of assembling a gypsum fiber wall (GVL) and hanging shelves on it, you can use a butterfly dowel or MOLLY (with significant weight). First, a metal base is created, which is fixed on concrete surface by means of dowel nails. The connection of the frame elements and GVL to each other is carried out by means of self-tapping screws. The main thing is to choose their color and take a rare step on the sheets of finishing material. Heavy products can be attached to the frame, not the GVL, which is fragile.
Anchor-bolt type of dowel
Such dowels are specialized specifically for fixing weighted items, including shelves of increased load or structures with a high load. For example, an M12 bolt is capable of supporting a weight of up to 2000 kg. The mechanism of operation of the cone-shaped anchor is as follows. When the anchor is screwed in, the metal spacer zone creeps onto the spacer clip and is pulled inward. Thus, the bolt is firmly clamped in the carrier material.
When carrying out repairs, self-tapping screws are an irreplaceable consumable. With their help, you can fix any structure on a specific surface. To securely fix the self-tapping screw in the material, you also need to use a dowel. The dowel is fixed at the base of the material, then a self-tapping screw is screwed into it. Dowels are plastic and metal. They always have a spacer in their design - an element that increases the adhesion of the fastener to the material.
Parameters for choosing a dowel for a self-tapping screw
For reliable fastening, you should choose the dowel for the self-tapping screw accurately and correctly. It is necessary to take into account the dimensions of the self-tapping screw and dowel, as well as the thickness of the product to be fixed. If the diameter of the screw exceeds the diameter of the dowel, the screw will break the dowel. If, on the contrary, the diameter of the dowel is greater than the diameter of the self-tapping screw, the spacers will not open completely and the fastening will not be strong enough. The same will happen if the screw is shorter in length than the dowel used.
The choice of a dowel must begin with its dimensional characteristics. Larger dowels are able to withstand heavy loads. Dowels of various diameters are designed for a specific load:
· 14 mm and more - very heavy load.
In addition to the dimensional characteristics, you need to know the density of the material in which the dowel is fixed. Dowels of the same size withstand heavy loads in denser materials. Also, the dowel is selected by type depending on the purpose of use and the structures to be fixed.
Types of dowels and screws for them
There are the following types of plastic and metal dowels:
· Spacer. These dowels are produced and used for fixing in concrete bases. The design of this dowel includes 2 or 3 spacers. Expansion dowels are used to attach lightweight parts. Such a dowel can be ideally fixed in a loose wall.
· Dowels of this type are made of metal, equipped with a large thread and a special drill. This helps to avoid pre-drilling the hole before installation. Not designed for heavy loads.
· Dowel nail . Consists of a plastic dowel and a steel nail for increased fastening strength. When driving in a nail, the dowel is firmly fixed in the material. This type is used for fixing metal profiles and skirting boards.
· Anchor. Such dowels are made of metal. They are in the shape of a cylinder. A nut is located at the base of the cylinder. When tightening the self-tapping screw, the nut opens the spacers in the hole, which ensures a solid fixation. Used when fixing massive components.
· Dowel-butterfly. Needed for hanging large items. The base, like the anchor dowel, has a nut. When tightening the self-tapping screw, the nut presses on the spacers that abut against inner surface products. As good for anchoring in a loose wall as an expansion dowel.
· Dowel-fungus. Dowels of this type are indispensable for thermal insulation work. With the help of them, the insulation is fixed on the surface of buildings.
After the choice of the desired type of dowel is made, it is necessary to select the corresponding self-tapping screw. With the help of a special table comparing the sizes of the dowel and the screw, you can find out how to choose the dowel for the screw.
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Attached material thickness (mm) |
Screw size (mm) |
For example, you have a dowel with a diameter of 10 mm and a length of 50 mm. The thickness of the material to be fixed is 10 mm. To find out how to choose a dowel for a self-tapping screw of the required size, refer to the table. With the given parameters, our dowel is suitable for a 6x60 self-tapping screw, as can be seen from the table. When fixing structures with a minimum material thickness, a dowel for a 3.5 mm x 25 mm self-tapping screw is suitable.
Using the above material, you can easily pick up a dowel for a self-tapping screw and perform the necessary work efficiently and professionally.
28.03.2016The modern market offers an extensive range of fasteners that allow you to solve any problems in the construction and other areas in various ways. This fully applies to dowels - domestic and foreign companies today offer dozens of dowels and related products. A large selection is, of course, good, but a wide assortment also creates a problem - even a specialist can find it difficult to choose fasteners that will most effectively solve the task.
The issues of choosing dowels, as well as their competent use, are discussed in this article. We hope that the information presented here will be useful and will help you make the right choice in any situation.
General look at the dowels: types, characteristics, features
The dowel is an auxiliary fastener that secures the main fastener (screw) in the supporting base. The use of a dowel facilitates installation, increases the strength and reliability of the connection, and prevents the destruction of the base material under the action of loads on the connection.
Three types of dowels can be distinguished, differing in the type of fixation at the base:
Dowels of the first type are fixed in the base material due to the action of friction forces. In such a dowel, a spacer part is provided, which, when the screw is screwed in, expands (wedges), rests against the walls of the channel, and is anchored. Previously, ordinary wooden dowels were used as expansion dowels, today they are made of plastic (usually nylon, polypropylene and polyethylene of various brands). Expansion dowels best withstand shear loads, therefore they are most often used for mounting on vertical surfaces (walls). They are not used for mounting suspended structures on horizontal surfaces (ceilings, consoles), as they do not resist pulling out poorly.
Dowels of the second type are fixed by creating a stubborn resistance outside or inside the base material. In such fasteners, it is structurally provided for the possibility of changing the shape during installation - expansion, tying into a knot, opening stops, etc. Due to this, the anchoring ("anchoring") of the dowel takes place, and it cannot be squeezed out. Anchor dowels work well for both shear and extrusion, so they are suitable for mounting on vertical and horizontal surfaces, including for hanging a variety of products from the ceiling.
Anchor dowels are divided into two groups:
With an external stop - used for mounting on thin-walled materials (gypsum board, fiberboard, MDF, etc.);
With internal stop - used for installation in both hollow and solid materials.
The dowels of the third type have a design that allows them to be used both as spacers and as anchors - it all depends on the base material. When installed in solid materials, the dowel works as a spacer, fixing itself due to frictional forces. When installed in hollow materials, the expansion part of the dowel is deformed (usually tied into a knot), due to which it is anchored.
There is also another type of fasteners - adhesive or chemical anchors. These products are fixed in the material using resin or special solutions.
It is necessary to make a remark about what a dowel and anchor are:
The dowel is an accessory product that can be used with a screw that is suitable for its characteristics (diameter and length). The dowel and screw are sold separately in most cases. Usually dowels are made of polymer materials (nylon, polyethylene), however, there are also metal dowels for screwing in metric screws;
Anchor is a finished product for which there is no need to purchase additional components. Usually anchors are made of metal, due to which high reliability and durability of installation based on them is achieved.
In the future, we will only talk about plastic dowels, their features, types and applications.
Features and benefits of plastic dowels
Plastic dowels are made from three main polymeric materials:
High or low pressure polyethylene (LDPE, HDPE);
Polypropylene (PP)
Nylon (polyamide-6, polyamide-66, PA).
Each of these materials has its own characteristics, advantages and applications, the main data are summarized in the table:
|
Mechanical properties |
Relation to moisture / water |
Chemical properties |
Temperature properties |
|
|
Polyethylene |
Strong, has high toughness (non-brittle), prone to aging, prone to cracking |
Has low hygroscopicity, water resistant |
Well resists the action of acids, alkalis, alcohols, oils, gasoline. Poorly withstands aromatics and chlorohydrocarbons |
Withstands temperature changes well, resistant to low temperatures down to -40 ° С |
|
Polypropylene |
Durable, hard, unbreakable, prone to aging and cracking |
Has low hygroscopicity |
Good resistance to acids, alkalis, gasoline, saline solutions, alcohols. Poor resistance to chloro-hydrocarbons. Permits odors |
It withstands temperature extremes well, works normally at temperatures up to +80 ° С, however, it has low frost resistance |
|
Nylon |
Solid, shock-resistant, has excellent antifriction properties, wear-resistant At its own moisture content 2 - 3% - viscous, at low humidity - brittle |
Hygroscopic (able to absorb up to 5% of its own weight of water), sinks in water |
Resistant to most acids, alkalis, alcohols, etc. However, it is poorly resistant to hydrochloric and sulfuric acids, ozone and hydrogen peroxide. |
Resistant to high and low temperatures, well withstand temperature extremes |
Based on this, you can give several recommendations on the use of dowels from different materials. Dowels made of PE and PP are best suited for interior work, and they can be used in rooms with high humidity, in aggressive environments (for example, at production sites of food, chemical and other enterprises), etc. However, it should be borne in mind that over time they lose their elasticity and can crack, therefore they are not suitable for critical high-load connections.
Nylon dowels are more resistant to temperature extremes, so they are well suited for outdoor use. However, here you should take into account the high hygroscopicity of this material - at high humidity, the dowel increases in volume, which can lead to an error during installation. Therefore, work on the installation of these dowels should be carried out at low air humidity, avoid work in the rain, during the spring thaw of snow, etc.
In general, today, in most cases, it makes sense to give preference to nylon dowels, however, one should take into account their higher cost and the dependence of the result on air humidity.
Metal anchors: advantages, disadvantages, applications
Metal anchors have one big advantage: they are able to work normally under significantly higher loads than plastic ones (at least 2 - 3 times, here the strength of the base material often comes to the fore, not the strength of the anchor). However, anchors are more difficult to manufacture and expensive, and most importantly, difficult to install. Therefore, today they are less used than plastic dowels.
The advantages of metal anchors include:
Durability;
The ability to attach suspended products to ceilings, consoles and other horizontal surfaces;
Fire safety.
However, anchors also have a number of disadvantages:
Complexity of installation;
High price;
Low resistance to corrosion (today they produce galvanized steel anchors and products from other corrosion-resistant materials, but under the constant influence of humidity, corrosive environments and temperature extremes, they lose their qualities).
Currently, metal anchors are used mainly for the most critical high-load connections, hanging various products on horizontal bases, etc.
Theory and practice of the selection of dowels and screws
To successfully solve the problem of installing a specific product, it is necessary to correctly select a dowel and a screw for it. The choice of the dowel is carried out taking into account three conditions:
Type and features of the base material;
Features of the assembled product;
Availability of the tool, planned labor costs, etc.
Based on the base material, you can choose several types of dowels:
Solid bases (concrete, ceramic and silicate bricks, natural and artificial stone) - universal and specialized (frame, dish-shaped, dowel-nails) expansion dowels;
Solid porous bases (aerated concrete, aerated concrete blocks) - spacer and screw dowels;
Hollow bases (slotted bricks, expanded clay concrete blocks, plates, etc.) - anchor dowels of various types, universal plastic dowels;
Thin-walled bases (gypsum board, fiberboard, MDF and others) - specialized anchor dowels of short length ("butterfly", Molly) and short screw dowels, self-tapping dowels (DRIVA).
Based on the features of the product being mounted, the selection of dowels is more diverse, here we will highlight only the most typical cases:
Shelves, cabinets, brackets, various wall structures, as well as lightweight ceiling structures - universal dowels for a wide range of applications;
Window frames, door frames, heavy facade and roof structures - special frame dowels of increased length;
Thermal insulation materials for facade and roofing - plate dowels of various types;
Hanging products, chandeliers, hanging structure components, stretch ceilings etc. –Anchoring dowels and anchors;
Cable channels, cable routes - specialized dowels with a countersunk head, dowels for clamps, dowel-clamps, etc.
For a successful installation, it is critical right choice the parameters of the dowel and the screw for it. A simple rule applies here: the larger the dowel, the greater the load it can withstand. Usually the maximum load is indicated by the dowel manufacturer.
The screw diameter is selected according to the recommendations of the dowel manufacturer. The selection of a screw for a dowel is performed based on a simple formula:
Lsh = d + Ld + A
Where Lsh is the theoretical length of the screw, d is the length of the pointed part of the screw (usually taken equal to the diameter of the screw), Ld is the length of the dowel, A is the thickness of the part to be mounted.
Typically, the theoretical screw length obtained is different from the standard length range, so choose a screw with a rounding up. Based on this, the drilling depth is also calculated - it must be equal to or greater than the actual length of the screw minus the width of the mounted product.
To maintain the strength characteristics and integrity of the base material, when using expansion dowels or anchor dowels with an internal stop, certain intervals must be observed between the dowels, as well as between the dowel and the edge of the base. The calculation is carried out based on the following parameters:
Drilling depth (h);
Distance between dowel axles (S);
Distance from the dowel axis to the edge / corner of the base (c);
Base thicknesses (d).
|
Base material |
c |
S |
d |
|
Concrete |
≥h |
≥2h |
≥2h |
|
Brick |
≥2h |
≥4h |
≥2h |
|
Aerated concrete |
≥2h |
≥4h |
≥2h |
However, the achievement of the required strength characteristics of the connection is possible only with proper installation.
Installation of plastic dowels: stages of work and features
For the successful installation of the dowel, it is necessary to prepare a hole taking into account the peculiarities of both the dowel itself and the base material.
When drilling a hole, it is necessary to take into account the peculiarities of the base and choose the mode that will allow you to achieve the required hole accuracy. Two cases are possible here:
Shockless drilling - used when working on hollow bricks, aerated concrete, thin-walled bases (GKL) and other materials prone to destruction;
Impact drilling (with varying intensity of impacts) - used mainly when working on concrete.
For non-hammer drilling, you should choose a drill of the same diameter as the dowel - this ensures tight installation and correct installation. However, when drilling strong materials with a hammer drill, you should use special drills with a diameter of 0.1 - 0.3 mm larger than the nominal. The fact is that due to the peculiarities of the drilling mode in concrete, the hole diameter decreases slightly, which is compensated by a special drill. Therefore, before starting work, you should decide on the selection of a drill for the dowel - this will prevent mistakes and reduce costs.
After drilling, the hole must be cleaned of drill meal and other contaminants. If this is not done, the particles remaining in the channel will replace the sliding friction force by the rolling friction force. That is, the dowel will roll along the particles, and this sharply reduces the strength of the connection and leads to accelerated squeezing of the dowel from the hole. When installing plastic dowels, in most cases it is sufficient to blow the hole with compressed air, although today special pumps are increasingly used.
The installation of the dowels should be carried out as recommended by the manufacturer. Here it should be borne in mind that plastic dowels are elastic and poorly resist shock loads (they can break, crumple), so they should be driven into the hole carefully, possibly using a mallet. Next, the screw is screwed in with a screwdriver or screwdriver.
Particular attention must be paid to the installation of double-expansion anchors, since orientation in the hole is critical for them: the expansion tabs must be oriented in the direction of the load (i.e., vertical). Otherwise, the dowel is deformed, as a result of which the expansion pressure and the strength of the entire fastening drop.
An overview of dowels and questions of their application
Consider the main types of dowels, their areas of application and installation features.
Spacer dowels. This is a large class of fasteners for solving a wide range of tasks in various fields (construction, decoration, assembly work). There are dowels of various lengths (standard, shortened, elongated), with two, three or four spacer lugs, with a countersunk head or with a rim, with additional elements for fixing and protection against rotation (tangential locking tabs), etc. The dowels have a standard range of diameters - 5, 6, 8, 10, 12, 14 and 16 mm, much less often dowels with a diameter of 4, 7 and 20 mm are produced.
For driving screws with a screwdriver or screwdriver;
For quick installation with a hammer - a dowel-nail.
Dowels are used for installation in solid materials (concrete, brick, stone) on vertical bases (walls), they can also be used for mounting lightly loaded products to ceilings.
Frame dowels... Specialized dowels for the installation of heavy structures in the presence of significant torsion and bending loads. They are used for mounting interior doors, window frames etc. Usually these are expansion dowels with an increased length (due to the increased length of the non-expansion part at the base), which allows for through installation. Such dowels can have one or two spacers, dowels of the second type can be used on hollow bases (they provide for the possibility of controlled deformation, due to which additional anchoring is performed in the base cavities).
Frame dowels are available in two main diameters - 8 and 10 mm, much less often you can find products with a diameter of 6 and 14 mm.
Dowels for aerated concrete... Specialized enlarged diameter dowels can be of two types:
Driven - installed in a drilled hole with a hammer;
Threaded - have a thread with which they are screwed into a drilled hole.
Hammer-in dowels have longitudinal screw elements that prevent turning when the screw is screwed in, and also increase the contact area with the base material (which also entails an increase in the friction force).
Anchoring dowels for thin-walled materials(Plasterboard, chipboard, etc.). There are several types of dowels - "Butterfly", Molly and others, but they all have essentially the same principle of operation. When the screw is screwed in, the back of the dowel, located on the back of the base, deforms and creates abutting surfaces, due to which anchoring occurs.
Threaded dowels for drywall... These are shortened threaded dowels that can be screwed into a drywall sheet, preventing it from collapsing. There are both conventional screw dowels and self-tapping dowels (DRIVA). In the latter case, the dowel does not require pre-drilling the hole, since it already has its own drill.
Universal dowels... These are expansion dowels, which, due to the design features of the expansion part (have weakened points of nodal fixation) and increased elasticity of the material, can also work as anchor. When installing the dowel on a sheet base, the back part is screwed onto a screw, tied into a knot - anchoring occurs. When installed in solid materials, the dowel works like a regular expansion plug.
Disc dowels. Specialized dowels for installation of facade and roofing thermal insulation materials... They have a large poppet head (usually from 45 to 90 mm), which ensures reliable fixation of thermal insulation. Dowels are available in two diameters - 8 and 10 mm. There are three types of disc dowels:
Spacer - plastic spacer nails are used for installation;
For a screw - various types of screws can be used for installation, usually used for work on sheet materials (profiled sheet);
Screw - threaded, can be used to install new layers of thermal insulation on top of old ones.
Specialized dowels for electrical work. A large group of dowels for the installation of cable channels, laying cable routes, etc. Most often, dowels for clamps, dowels-clamps, dowels with a countersunk head for cable channels, dowels for mounting clips for pipes (smooth and corrugated), etc. are used.
In general, there is a wide variety of dowels on the market today, so it is not difficult to choose the right option among them.
12.05.2015
Many are faced with the problem of selecting a dowel for a self-tapping screw, when it is necessary to fix any structure to concrete, brick, aerated concrete or drywall using a self-tapping screw, but in this case you cannot do without a dowel.
It is necessary to take into account the diameter and length of the self-tapping screw, and the diameter and length of the dowel, and the thickness of the material to be attached. If the dowel is less than the prescribed diameter, then the self-tapping screw will break it, if it is larger, then the self-tapping screw will not open it properly and there will be no reliable installation, the same will happen if the self-tapping screw does not reach the end of the dowel. So how, after all, to choose the right screw and dowel?
You need to start the selection with the dowel, with its size (diameter, length). The larger the size of the dowel, the more load it can withstand. The smallest diameters are 4 mm and 5 mm, designed for light loads, 6 and 8 mm for medium, 10 and 12 mm for heavy loads, 14 and 16 mm for very heavy loads, for fastening scaffolding, etc. You should also take into account the density of the material in which the dowel will be located. The denser the material, the greater the load the dowel of the same size can withstand.
After we have selected the required size of the dowel, you can choose a self-tapping screw for it.
For a dowel with a diameter of 4 mm, a self-tapping screw with a diameter of 2 mm is suitable.
For a dowel with a diameter of 5 mm, a self-tapping screw with a diameter of 2.5 mm is suitable. (from 2 mm to 3 mm.)
For a dowel with a diameter of 6 mm, a self-tapping screw with a diameter of 4 mm is suitable. (3.5mm to 4.5mm)
For a dowel with a diameter of 8 mm, a self-tapping screw with a diameter of 5 mm is suitable. (4.5 mm to 5.5 mm)
For a dowel with a diameter of 10 mm, a self-tapping screw with a diameter of 6 mm is suitable. (5.5mm to 6.5mm)
For a dowel with a diameter of 12 mm, a self-tapping screw with a diameter of 8 mm is suitable. (6.5 mm to 8.5 mm)
For a dowel with a diameter of 14 mm, a self-tapping screw with a diameter of 10 mm is suitable. (8.5 mm to 10.5 mm)
For a dowel with a diameter of 16 mm, a self-tapping screw with a diameter of 12 mm is suitable. (10.5 mm to 12.5 mm)
Well, we have selected the required size of the dowel, selected the required diameter of the screw for it, now it only remains to choose the required length of the screw.
For this, the length of our dowel is taken, the thickness of the material to be attached is added and we get the required minimum length of the self-tapping screw. The thickness of the material to be fastened should not be more than 35% in loose bases, and not more than 60% in dense bases of the length of the dowel.
The self-tapping screw can come out of the dowel a little, this is not scary, the main thing is that it must go to the end of the dowel and fully open it, for reliable installation, if it is not screwed in completely, then the dowel can turn, and the installation will not be reliable. You need to drill a hole for the dowel a little more than its length and the same diameter.
For example: we need to fix 20 mm plywood to concrete floor... To do this, we take an 8x50 dowel (8 mm dowel diameter, 50 mm its length), and to it a 5x70 self-tapping screw (5 mm screw diameter, 70 mm its length). For drilling, we need a drill 8x110 (8 mm diameter, 110 mm total drill length, 80 mm working part length). You need to drill to a depth of at least 60 mm. After drilling, the hole is cleaned of dust, a dowel is inserted, then a self-tapping screw is screwed into it through the plywood.
Correspondence table of screws and dowels
|
Dowel diameter (mm.) |
Dowel length (mm.) |
Attached material thickness (mm) | Self-tapping screw size (mm.) |
| 5 | 25 | 5 | 3x30 |
| 5 | 25 | 10 | 3x35 |
| 6 | 25 | 5 | 4x30 |
| 6 | 30 | 5 | 4x35 |
| 6 | 30 | 10 | 4x40 |
| 6 | 35 | 10 | 4x45 |
| 6 | 35 | 15 | 4x50 |
| 6 | 40 | 10 | 4x50 |
| 6 | 40 | 15 | 4x60 |
| 6 | 40 | 20 | 4x60 |
| 6 | 50 | 10 | 4x60 |
| 6 | 50 | 15 | 4x70 |
| 6 | 50 | 20 | 4x70 |
| 8 | 30 | 5 | 5x35 |
| 8 | 30 | 10 | 5x40 |
| 8 | 40 | 10 | 5x50 |
| 8 | 40 | 15 | 5x60 |
| 8 | 50 | 10 | 5x60 |
| 8 | 50 | 20 | 5x70 |
| 8 | 60 | 10 | 5x70 |
| 8 | 60 | 20 | 5x80 |
| 8 | 60 | 30 | 5x90 |
| 8 | 80 | 10 | 5x90 |
| 8 | 80 | 20 | 5x100 |
| 8 | 80 | 30 | 5x120 |
| 10 | 50 | 10 | 6x60 |
| 10 | 50 | 20 | 6x70 |
| 10 | 60 | 20 | 6x80 |
| 10 | 60 | 30 | 6x90 |
| 10 | 80 | 20 | 6x100 |
| 10 | 80 | 40 | 6x120 |
| 10 | 80 | 60 | 6x140 |
| 10 | 100 | 40 | 6x140 |
| 10 | 100 | 50 | 6x150 |
| 10 | 100 | 60 | 6x160 |
| 12 | 70 | 10 | 8x80 |
| 12 | 70 | 20 | 8x90 |
| 12 | 70 | 30 | 8x100 |
| 12 | 100 | 20 | 8x120 |
| 12 | 100 | 40 | 8x140 |
| 12 | 100 | 60 | 8x160 |
| 12 | 120 | 40 | 8x160 |
| 12 | 120 | 60 | 8x180 |
| 12 | 120 | 80 | 8x200 |
| 14 | 75 | 25 | 10x100 |
| 14 | 75 | 35 | 10x120 |
| 14 | 100 | 20 | 10x120 |
| 14 | 100 | 40 | 10x140 |
| 14 | 100 | 60 | 10x160 |
| 14 | 135 | 25 | 10x160 |
| 14 | 135 | 35 | 10x180 |
| 14 | 135 | 45 | 10x180 |
In this article, we showed you how to choose the right screws for the dowel. If you still have questions, please contact our online store KREP-KOMP, by phone, email, skype. Our managers will be happy to advise you on all issues!
