Square head / headrest Bolts

Bolts with a square head or square neck are used where it is important to prevent the fastener from turning during installation. The special shape of the head or neck allows the bolt to be held in place whilst the nut is being tightened, which simplifies installation and ensures a secure connection.

The range includes bolts with a square undercut and models with a fully square head. They differ in design and area of application, so when selecting them, it is important to consider the type of joint, the material of the components, the load and the operating conditions.

What is a square-head bolt / undercut bolt

А square-head bolt is a fastener with a square-shaped head. This design prevents the bolt from rotating whilst the nut is being tightened.

In bolts with a square undercut, the head is usually semi-circular in shape, with a square element located directly beneath it. Once installed, this element fits into the corresponding hole in the material and prevents the shank from turning.

Such fasteners are used in the manufacture of metal and timber structures, mechanical engineering, furniture production, agricultural equipment and other sectors where parts need to be joined without the need to hold the head in place with a spanner.

Design features of square-head bolts
The main feature of this type of fastener is the square element in the head, which acts as an anti-rotation device. Its shape and dimensions depend on the specific standard.

Bolts with a square underhead are characterised by a combination of a half-round head and a square underhead. For example, DIN 603 specifies the design of bolts with a half-round head and a square underhead. Such models are often used in applications where the head must have a smooth external surface after installation.

A square-head bolt differs in design from this model: it is the head itself that is square, rather than a separate square socket. The DIN 479 standard, in particular, applies to such products.

When selecting bolts, the following factors are taken into account:

• the diameter and length of the bolt;
• the type of head;
• the material of manufacture;
• the strength class, if specified by the standard;
• the presence and type of protective coating;
• the operating conditions of the joint.

For assembly, the bolt is used in conjunction with a nut and, where necessary, a washer of the appropriate size.

Advantages of square-head fasteners

The design of square-head bolts with a shoulder offers several practical advantages.

Prevention of rotation. The square element holds the bolt in place whilst the nut is being tightened. This is particularly useful during assembly when access to the head is restricted.

Convenient installation. In many cases, there is no need to hold the bolt head in place with a tool at the same time. This reduces the number of steps required during assembly.

Various designs. Bolts are available in a range of diameters, lengths, materials and finishes, so they can be selected to suit a specific joint.

Versatile application. Depending on their design and specifications, these fasteners are used in timber, metal and composite structures, as well as in industrial equipment.

Corrosion protection. For use in suitable environments, bolts with an anti-corrosion coating or made from stainless steel can be used.

If you need to buy bolts with a square socket head, when placing your order you should check not only the diameter and length, but also the standard and the head design. This will help to avoid the fastener not fitting the mounting hole.

Which bolt should you choose – one with a square head or one with a square socket head?

The choice depends primarily on the design of the assembly and the method of installation.

A bolt with a square neck is best used when a smooth, semi-circular head is required and the fastener needs to be secured in the hole by means of the square neck. Such products, in particular DIN 603, are widely used in assemblies where the nut is accessible from one side.
Bolts with a square head have a different head geometry and can be used in assemblies where this shape is specified by the design or a standard.
It is not sufficient to compare these products solely on the basis of diameter and length. Before purchasing, it is necessary to check the standard, the dimensions of the head and square neck, the material, the strength class and the operating conditions.
For mass production or regular procurement, it is also important to maintain consistent fastener specifications across batches.

Benefits of purchasing on the Dinmark B2B platform

For businesses that regularly procure fasteners, ease of ordering and access to technical information are just as important as the product range itself.
On the Dinmark B2B platform, you can select square-head bolts in bulk and square-head models according to your required specifications.
The following are available to wholesale customers:
1️⃣ a wide range of sizes;
2️⃣ information on product specifications and standards;
3️⃣ up-to-date delivery terms;
4️⃣ the option to reorder required items;
5️⃣ documents and order information in your personal account;
6️⃣ an additional 2% discount on orders placed via the website. 

If a company requires square-head bolts in bulk for regular supply, the order details can be drawn up in accordance with the production specifications and the required quantities.

Questions and Answers

How does a bolt with a square undercut head (DIN 603) differ from a bolt with a fully square head (DIN 479)?

The main difference lies in the shape of the head and the method of securing it. DIN 603 uses a semi-round head with a square undercut beneath it. In DIN 479, the head of the bolt itself is square. Therefore, these products are not always interchangeable: the design of the hole and the requirements for the assembly must be taken into account.

What determines the price of square-head bolts?

The cost depends on the size, material, strength class, coating, standard, manufacturer and order volume. For bulk purchases, the number of items in the batch is also a factor.

Is a bolt with a square undercut suitable for metal structures, or is it only for timber?

This type of bolt is not limited to use in timber. It can also be used in metal structures, provided the hole geometry, material thickness and fastener specifications meet the requirements of the specific joint. DIN 603 is often associated with timber and furniture structures, but its scope of application is broader.

Can square-head bolts be ordered throughout Ukraine with delivery?

Yes, Dinmark delivers fasteners throughout Ukraine. The terms and delivery times depend on product availability, order volume and delivery method.