Anchor bolt with nut - for fastening heavy structures!

The wedge anchor for concrete has the best holding capacity among mechanical type expansion fasteners, which allows it to be used for heavy and medium loads. It consists of a threaded stud at one end and a spacer at the other. The fastener comes with a nut and washer. When the nut is tightened, the tapered shank is pulled into the collet sleeve, wedging it apart and thereby ensuring rigid fixation in the hole.

How does an anchor fastener with a nut work?

Taking into account the fact that this fastening mechanism must hold quite heavy elements, it was carefully thought out and redesigned. The main structural element in it is a spacer pin, which has a cone shape at one end, and a metric thread is cut at the other end, onto which a nut is screwed. The entire length of the stud, except for the threaded part, is fitted with a special metal sleeve with slots.

This device works on the principle of “expansion”, that is, when we start to tighten the nut, the cone-shaped end enters the sleeve and expands it in the hole. A distinctive feature is that such an anchor has a cast pin, which is much stronger than other anchor structures. Well, and, of course, we forgot to mention the nut and, without fail, the lock washer, which are screwed on from the thread side. The washer does not allow the nut to go deeper into the hole when tightening.

In some cases, during fastening, installers use a second washer as an additional lock, which closes the hole at the installation site, but this approach depends on the specific installation conditions. The scope of application of such fasteners can be quite different: from the installation of stair railings to heavy metal structures. The most popular application today is the installation of brackets for air conditioning. The device itself has quite a decent weight, so the use of such a mount is completely justified.

Mounting options

Installation instructions

1. A hole in the concrete base is drilled with a drill with a carbide tip using a hammer drill or impact drill.
2. Before installing the dowel, it is important to thoroughly clean the hole from drill chips, first using a metal brush and then a purge pump.
3. Screw the nut onto the threaded end of the stud, placing a washer underneath it. Align the top of the nut with the end of the stud. This is done to protect the start of the thread from damage by a hammer.
4. Insert the fastener through a hole in the part to be attached (through-hole installation) or directly into the material (pre-assembly) and drive it in with a hammer.
5. Screw the nut first by hand until the washer fits snugly against the surface, and then tighten it with a wrench, making 3-5 turns.

Technical characteristics of anchor bolts

Technical documentation recommends installing such fastenings in solid solid materials, such as concrete, solid brick, natural stone. In each individual case, we must choose a bolt and nut whose dimensions will provide us with high-quality fastening. But it is worth remembering that during installation, when tightening the nut, the stud moves forward a certain distance; as a result, sometimes this length creates an obstacle when installing the products that we are fastening.

Today in stores you can find fasteners of almost any length, for various types of tasks. As a rule, the line of anchor fastenings begins with a stud size of 18 millimeters. The longest fastener reaches 400 millimeters in net size of the fastening pin. Accordingly, depending on the length, we also have different diameters; this value is calculated by the diameter of the sleeve for which the hole is drilled.

The diameter of the bushing usually starts from 6.5 millimeters, this is, as a rule, the smallest anchor; gradually, as the length increases, the diametrical value also increases; on the longest fastening, the bushing can be 20 millimeters in circumference, and such fasteners can withstand quite significant loads. If you are interested in the holding force of such fasteners, you can find it out from the technical documentation, we talked about it earlier.

Reinforced version - double-spacer fastener

Due to the fact that consumer requirements are constantly growing, and there is a need for the installation of fairly heavy structures, it was decided to slightly modify the fasteners. This is how a modified product appeared on the building materials market - an anchor bolt with a double-spacer nut. This technology has made it possible to sufficiently increase the holding force of such fastenings.

The design itself is the same pin, but in this case two bushings are used as a holding mechanism, one of which is wedge-shaped and fits into the second bushing. Thus, by tightening the nut, we increase the holding properties, evenly distributing the force along the entire length of the fastener. The double-spacer anchor with a ring uses the same technology in its design, and, as practice shows, quite successfully.

This modified fastening is used mainly in production, but not only in the construction environment. For example, very often this mounting element is used to fasten machine tools in workshops. Usually, during operation, the machine creates a certain vibration, which, as a rule, is not needed, and if previously the machine was simply attached to the floor using concrete, today the easiest way is to use a universal mount and get rid of unwanted vibration during operation.

Wedge anchor

It is a special wedge nut installed inside the hole, with a sleeve installed on top. When the bolt is tightened, the nut, trying to come out, wedges the sleeve and is firmly held inside the hole.

This design is a bushing with a conical hole inside and a thread. When screwing in the anchor, the sleeve wedges into the hole and is thus fixed.

Expandable butterfly anchor. The main feature is that it can be installed in through holes, as well as in the case of thin-walled bases. The principle of operation is based on the deformation of the middle part and the opening of the petals when screwing in the anchor.

Expansion anchors. This is the most common type and does not require particularly careful adherence to the hole dimensions. The principle of operation is based on the expansion of the bushing when a pin with a cone-shaped or spherical thickening at the end is pulled out of it during the process of screwing a nut onto it and pulling it out.

So, we have indicated the main types of anchors used in practice. In some specific situations, special fasteners are required; according to the underlying principles of operation, they are similar to those discussed, but they have design features, and therefore two of their varieties are presented below, as an example.

How to properly install an anchor bolt with a nut - step-by-step diagram

Step 1: Anchor Hole Diameter

Before drilling a hole for the fastening, you need to select a concrete drill for a hammer drill of the required diameter. In this case, first of all, be guided by the dimensions of your mount. It is under no circumstances recommended to drill a hole if the bushing does not fit into it. It is better to go through the same diameter drill again, and the hole will become a little larger. If you drill out the fastening point with a drill of a larger diameter, the bushing can freely “walk” in it, while the spacer mechanism simply cannot perform its holding functions.

Step 2: Clear the mounting area of ​​debris

It is no secret that after drilling, debris remains in the finished hole after using a hammer drill. It is these crumbs and dust that interfere with the installation of the bolt at the installation site. It is especially difficult to install a double-spacer mechanism into an uncleaned hole; such fasteners have a sleeve that is slightly wider than usual. Therefore, before installation, thoroughly clean the hole; if necessary, use a construction or household vacuum cleaner.

Step 3: Correct installation of heavy elements

After you have inserted the bolt into the hole, do not rush to mount your device while tightening the nuts; there is a more practical solution. After installing the anchor, without hanging the product, tighten the bolt with a wrench until it stops. Tightening must be carried out until the pin opens the bushing, and the fastening, so to speak, assumes operating mode. After this, you can place the nut on the studs, which are already firmly held in the mounting hole, install the device, and calmly tighten it with the nuts.

• Author: Mikhail Malofeev
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Types of anchor bolts and areas of their application

A fastener such as an anchor bolt is presented on the modern construction market in various designs. Along with universal fasteners of this type, manufacturers produce anchor bolts designed to solve highly specialized installation problems.

In order to choose the right fastener of this type, it is necessary not only to have a good understanding of its varieties, but also to know what types of anchors are used in certain cases. Let's consider the most popular types of anchor fasteners, their scope of application and the validity of their choice in a particular situation.

With a nut
This is the simplest anchor, consisting of a threaded rod with a conical lower end, a spacer sleeve with longitudinal side slots and a nut, with which such a bolt is fixed in the mounting hole. The principle of operation of such a fastening device is quite simple: its entire structure is placed in a pre-prepared hole, the diameter of which must correspond to the transverse size of the spacer sleeve; when the nut is tightened, the threaded element begins to be drawn into the hole of the spacer sleeve, spreading it apart with its conical tip. Thus, the spacer sleeve, which has increased in diameter, ensures reliable fastening of the anchor bolt in the mounting hole.

Anchor bolts are made from various steels for fastening in dry places, with high humidity and for use in aggressive environments

Modern industry produces anchor bolts equipped with a nut in a wide range of sizes. Thus, the minimum diameter of such fasteners corresponds to 6 mm, and the maximum can reach up to 28 mm. As for the length, it can be in the range of 60–300 mm. When choosing such an anchor, you should keep in mind that it will be effective only in cases where fastening with its help is carried out in building materials with a dense internal structure (this includes concrete, natural stone, solid brick, etc.).

With hook

An anchor bolt of this type differs from the previous one only in that its upper part is crowned not by a straight threaded end, but by a hook, which makes it easy to install various attachments. The nut, also used in the design of such an anchor and located directly under its hook, is necessary only to ensure the expansion of the spacer sleeve and, accordingly, its reliable fixation in the wall or any other building structure.

Technical parameters of hook anchor bolts (click to enlarge)

The main convenience of this anchor bolt is that the object attached to its hook can be removed at any time if the need arises. Anchors of this type are most often used for mounting lamps and chandeliers, attaching water heaters and other household devices to wall surfaces.

With ring

This anchor differs from the previous one in that its upper part is crowned not with a hook, but with a ring or half-ring. Moreover, the principle by which it works is similar to the action of anchor bolts of the two previous types. The ring that ends the upper part of such fasteners is very convenient to use for mounting various objects and structural elements.

The anchor bolt with ring is protected by a white or yellow anti-corrosion coating

The dimensions of the structural elements of the anchor bolt with a ring can be different. It is successfully used for hanging various objects on ceiling structures; with its help it is very convenient to perform various stretches, attach cables, chains, cable routes, scaffolding, etc.

Double-spacer

Such anchors differ from conventional expansion anchors in that their design contains two bushings at once, which expand during the process of tightening the threaded element. The principle of operation of double-spacer anchor bolts is that when the screw is tightened, one of the spacer sleeves enters the second, spreading it apart. In this case, the first bushing into which the screw is screwed is also unclenched. Due to the larger area of ​​adhesion to the walls of the mounting hole provided by such an anchor bolt, it can be used for installation in porous and even hollow building materials.

Types of double-expansion anchors
Wedge
Wedge-type anchors, due to their high cost, have not found widespread use either in construction or during repair work. Their price is explained by the complexity of their design, which can be assessed even from the photo. When screwed, the screw of such an anchor bolt acts on a wedge element that moves freely along the inside of the hole in the spacer sleeve. It is the latter, exerting pressure on the spacer sleeve from the inside, that ensures its maximum expansion.

The wedge-type anchor bolt is considered a modernization of the standard anchor.
Driven In
, it is not the screw that is responsible for loosening the spacer sleeve of the anchor bolt, the design of which is fundamentally different from the design of all of the above, but a special impact device, which is often simply called a nail. The process of attaching such an anchor to a building structure is as follows. Only a bushing is placed in the mounting hole in the building structure, which is expanded by applying a special impact element to it. After the spacer sleeve is securely fixed in the hole, the impact element is removed from it and a bolt or pin is screwed in instead, onto which the object being fixed is hung.

Dimensions and parameters of drive-in anchors (click to enlarge)
With hex head
The main element of this type of fastener is a regular bolt, which is inserted into a cone-shaped hole in the spacer sleeve. By expanding the hole, the anchor bolt thereby expands the petals of the spacer sleeve, ensuring its reliable fixation in the mounting hole. A variety of such fasteners are anchors, on the top of which there are slots for a Phillips screwdriver. Taking into account the fact that a screwdriver cannot provide the same force as a wrench, anchors of this type are made only in small sizes (their diameter, as a rule, does not exceed 12 mm).

Parameters of hexagonal anchor bolts (click to enlarge)

Thus, there are a variety of types of anchors on the modern market. The main requirement for them is high reliability of fastening, so they should be selected taking into account not only the size and weight of the object being fixed, but also the strength characteristics of the building structure material and a number of other parameters.