Expansion bolts according to DIN 2510 – For heavy-duty screw connections with expansion shaft
What are expansion bolts?
Expansion bolts are specially designed fasteners that expand elastically under axial preload. This targeted longitudinal expansion reduces the stress on the thread and increases operational reliability—especially in dynamic or thermally stressed applications.
They belong to the group of bolts with expansion shafts and are frequently used in bolted connections with expansion shafts, for example in:
- Turbomachinery
- Internal combustion engines
- Steam boilers
- Flange connections in pipeline construction
The above-mentioned properties make expansion bolts and expansion screws an ideal solution for precise and secure connections in industry. They are particularly suitable for structures that are subject to changing operating forces and temperatures and where the durability of the bolt connection must be ensured. The favorable behavior of expansion bolt connections is based on their elasticity, in particular on the fact that they exhibit a greater elastic change in length than so-called rigid bolt connections with the same preload.
This behavior leads to a number of advantages:
- Expansion bolts have a high level of durability, as the additional loads on the bolts due to changing operating forces, thermal expansion, and bending moments are reduced.
- The preload drop, which contributes significantly to the loosening of screw connections—during operation due to creep of the material, settling phenomena in the force-transmitting surfaces of the connection and the clamped parts, as well as bending of the threads—is lower.
- Under certain conditions, the amount of preload applied can be easily measured by the change in length of the screw.
Applications of expansion bolts in industry
Expansion bolts have a wide range of applications. They are frequently used in mechanical engineering, vehicle construction, shipbuilding, aircraft construction, and many other branches of industry. There, they are used to connect components that are exposed to high loads.
A major advantage of expansion bolts is their flexibility. They can adapt to different loads, ensuring an optimal connection. This is particularly important in applications where loads can change during operation. Expansion bolts can expand and contract to compensate for these loads and keep the connection stable.
Another advantage of expansion bolts is their high precision. The expansion of the bolt creates uniform and controlled preload, which ensures a secure connection. This is particularly important in applications where high accuracy and reliability are required, such as in the aerospace industry.
The quality of expansion bolts is a decisive factor in their performance. Our expansion bolts are made from high-quality materials and manufactured under strict quality controls. This enables us to guarantee high load-bearing capacity and a long service life.
In summary, expansion bolts offer maximum flexibility and are the perfect solution for precise and secure connections in industry. Their versatile applications and outstanding quality make them a reliable choice for demanding applications.
Technical features of expansion screws
Geometry and structure of expansion bolts
The functionality of an expansion bolt depends largely on its geometry and material:
- Expansion shaft length: At least 2 to 4 times the nominal diameter (d). A longer expansion shaft increases the elasticity of the connection.
- Transition radius: A generous radius between the shaft and thread reduces stress peaks.
- Shaft diameter (ds): Approximately 90–95% of the thread core diameter. This makes the shaft the main expansion zone.
Materials and strength
- Materials: High-strength steels such as 42CrMo4, 21CrMoV57, or stainless variants (e.g., X5CrNi18-10) – depending on temperature and corrosion requirements.
- Tensile strength: Typically 800–1100 MPa, depending on design and standard.
The following aspects must be taken into account when designing expansion screws and expansion bolts:
- The minimum length of the expansion shaft for expansion screws should be at least twice, ideally four times, the thread diameter to ensure sufficient elasticity.
- The ratio of thread core diameter to expansion shaft diameter should be approximately 1.1 in order to optimize the load-bearing capacity and elasticity of the screw.
- The transition angle between the expansion shaft and the thread should be kept relatively small. This results in a favorable flow of force and better load distribution in the screwed thread.
Advantages of expansion bolts
The main advantage of expansion bolts and expansion screws is that they enable even load distribution across the connection and offer high strength. They are often used in applications where a reliable and durable connection is required, such as in the construction industry, mechanical engineering, and vehicle manufacturing.
It is important to note that expansion bolts and expansion screws must be carefully dimensioned and correctly tightened to ensure a safe and reliable connection. You can find more information on this in our expertise guide.
- Constant preload: Lower setting losses due to elastic longitudinal expansion.
- Greater operational safety: Less risk of bolt loosening with changing loads.
- Measurable preload: The change in length can be used to check the preload force.
- Standard-compliant design: In accordance with DIN 2510 - for standardized quality and interchangeability.
Further advantages of expansion bolts in accordance with DIN 2510 are:
- Flexibility: Lower setting losses due to elastic longitudinal expansion.
- Precision: The expansion of the screw creates uniform and controlled preload. This ensures a secure connection that remains stable even under high loads.
- Reliability: Expansion screws are characterized by high load-bearing capacity and durability. They can absorb high forces and provide a reliable connection that withstands even extreme conditions.
- Easy installation: Expansion bolts are quick and easy to install. They do not require complex preparatory work such as attaching washers or adjusting the preload.
- Ease of maintenance: Expansion bolts allow for easy maintenance and inspection. If necessary, they can be easily replaced without having to remove other components.
Differences between expansion bolts and expansion screws
Expansion bolts and expansion screws according to DIN 2510 are fasteners used to create a secure connection between two components. The main difference between expansion bolts and expansion screws lies in their design and function.
Expansion bolts are special bolts that are highly resistant and expand when tightened. They consist of an elongated body with a thread on one side and a conical end on the other. When the nut is tightened on the threaded end, the bolt expands, creating a secure connection between the components. Expansion bolts are often used in conjunction with a special expansion nut to create the required expansion and secure the connection.
Expansion screws, on the other hand, are bolts that lengthen when tightened. They have a special thread profile that allows for axial expansion. When the nut is tightened onto the bolt, the bolt lengthens, creating a secure connection between the components. Expansion bolts are often used in conjunction with a special expansion nut to create the necessary expansion and secure the connection.
| Characteristic | Expansion screws | Expansion bolts |
| Usage | Frequently used in engines, cylinder heads, turbines, or other high-stress connections. | Mostly in mechanical engineering or for flange connections. |
| Function | Expansion screws are elastically stretched when tightened and generate a defined preload. | Expansion bolts are also stretched elastically, but they are often part of a bolt connection with a nut. |
| Advantages | Repeatable preload, reduced risk of loosening, improved force distribution. | Expansion bolts are usually not threaded along their entire length. They can be used multiple times, depending on the application and load, and are often larger in size and designed for higher forces. |
| Special feature | Often only usable once, as plastic deformation alters its properties. | Robust and often reusable. |
Standards and variants according to DIN 2510
We offer expansion screws in various shapes – depending on requirements:
- Shape L: Standard design with cylindrical expansion shaft
- Shape Z / ZU: With extended shaft for defined expansion zone
- Shape K / KU: With head or spacer pin – ideal for flanges
- Shape NF: For potentially explosive areas (non-sparking)
Expansion bolts are used in various industries, including:
Mechanical engineering: Expansion bolts are used to connect machine components such as gears, shafts, and bearings.
Vehicle manufacturing: In the automotive industry, expansion bolts are used to securely fasten engines, transmissions, and other components.
Shipbuilding: Expansion bolts are used to connect ship components such as hull plates, decks, and structures.
Aircraft manufacturing: In the aviation industry, expansion bolts are used to secure aircraft structures such as wings, landing gear, and engines.
The advantages of expansion bolts in detail are:
Flexibility: Expansion bolts can expand and contract under load to adapt to different loads. This ensures an optimal connection, even if the loads change during operation.
Precision: The expansion of the bolt creates uniform and controlled preload. This ensures a secure connection that remains stable even under heavy loads.
Reliability: Expansion bolts offer high load-bearing capacity and a long service life. They are able to absorb high forces and provide a reliable connection that can withstand even extreme conditions.
Easy installation: Expansion bolts are quick and easy to install. They do not require any time-consuming preparatory work such as fitting washers or adjusting the preload.
Ease of maintenance: Expansion bolts allow for easy maintenance and inspection. If necessary, they can be easily replaced without having to remove other components.
Overall, expansion bolts offer a reliable and precise solution for connections that are subject to heavy loads. Their flexibility, precision, and reliability make them a popular choice in various industries.
| DIN 2510 Form L is a special standard for expansion bolts defined by the German Industrial Standard (DIN). It defines the requirements for expansion bolts, in particular with regard to their dimensions, materials and mechanical properties. According to the standard, expansion bolts must have a certain geometry that allows them to expand under load. They must have an extended thread area, known as the expansion area. This expansion area allows the bolt to expand under load and thus create a uniform and controlled preload. DIN 2510 Form L also stipulates that expansion bolts must be made of high-strength materials in order to be able to withstand high loads. As a rule, they are made of alloy steel or stainless steel. The exact material requirements are specified in the standard. In addition, DIN 2510 Form L specifies the mechanical properties of expansion bolts, such as the minimum tensile strength, the minimum yield strength and the minimum elongation. These properties ensure that the expansion bolts meet the requirements for strength and reliability. DIN 2510 Form L is an internationally recognized standard for expansion bolts and is used by many manufacturers and users worldwide. It ensures that expansion bolts have a uniform quality and performance and can be used safely in various applications. | |||||||||||
| Thread (d1) | M12 | M16 | M20 | M24 | M27 | M30 | M33 | M36 | M39 | M42 | M45 |
| d2 | 8,5 | 12 | 15 | 18 | 20,5 | 23 | 25,5 | 27,5 | 30,5 | 32,5 | 35,5 |
| d3 | 8 | 12 | 14 | 14 | 18 | 18 | 25 | 25 | 28 | 28 | 32 |
| b1 | 20 | 23 | 28 | 32 | 35 | 39 | 42 | 45 | 48 | 52 | 55 |
| z1 | 1,75 | 2 | 2,5 | 3 | 3 | 3,5 | 3,5 | 4 | 4 | 4,5 | 4,5 |
| z2 | 4 | 5 | 6 | 6 | 6 | 6 | 9 | 9 | 10 | 10 | 11 |
| SW | 7 | 10 | 11 | 11 | 13 | 13 | 22 | 22 | 24 | 24 | 27 |
| DIN 2510 Form NF is a special version of expansion bolts manufactured in accordance with the German Industrial Standard (DIN) 2510. The designation "NF" stands for "non-flame-retardant" and refers to the specific requirements for expansion bolts used in potentially explosive atmospheres. DIN 2510 Form NF specifies special requirements for the design and material of expansion bolts to ensure that they comply with explosion protection requirements. This includes the use of materials that do not generate sparks and the prevention of potential ignition sources. DIN 2510 Form NF expansion bolts are often used in industries such as the chemical, oil and gas, petrochemical and other potentially explosive environments. They provide a safe and reliable connection that meets the high safety standards in these areas. | |||||||||||
| Thread (d1) | M12 | M16 | M20 | M24 | M27 | M30 | M33 | M36 | M39 | M42 | M45 |
| d2 | 21 | 26 | 31 | 35 | 40 | 45 | 49 | 53,5 | 58,5 | 63,5 | 68,5 |
| d3 | 14,5 | 18,5 | 22,5 | 26,5 | 30,5 | 33,5 | 36,5 | 39,5 | 42,5 | 45,5 | 49,5 |
| m | 12 | 16 | 20 | 24 | 27 | 30 | 33 | 36 | 39 | 42 | 45 |
| s | 22 | 27 | 32 | 36 | 41 | 46 | 50 | 55 | 60 | 65 | 70 |
| t | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| DIN 2510 Form Z is a specific design of expansion bolts manufactured in accordance with the German Industrial Standard (DIN) 2510. It defines the requirements for expansion bolts, including their dimensions, materials and mechanical properties. The form Z characterizes a special variant of expansion bolts that have an extended shank and an extended thread. This design allows for greater elongation of the bolt under load, resulting in a more uniform and controlled preload. DIN 2510 Form Z is often used in areas where high accuracy and reliability are required. It is often used in the engineering, automotive and aerospace industries to join components that need to withstand heavy loads. | |||||||||||
| Thread (d1) | M12 | M16 | M20 | M24 | M27 | M30 | M33 | M36 | M39 | M42 | M45 |
| d2 | 8,5 | 12 | 15 | 18 | 20,5 | 23 | 25,5 | 27,5 | 30,5 | 32,5 | 35,5 |
| d3 | 8 | 12 | 14 | 14 | 18 | 18 | 25 | 25 | 28 | 28 | 32 |
| b3 | 27 | 31 | 36 | 42 | 47 | 50 | 53 | 57 | 60 | 64 | 66 |
| z1 | 1,75 | 2 | 2,5 | 3 | 3 | 3,5 | 3,5 | 4 | 4 | 4,5 | 4,5 |
| SW | 7 | 10 | 11 | 11 | 13 | 13 | 22 | 22 | 24 | 24 | 27 |
| DIN 2510 Form K specifies a particular type of expansion bolt that meets the requirements of the German Industrial Standard (DIN) 2510. This standard specifies the requirements for expansion bolts, including their dimensions, materials and mechanical properties. Form K refers to a special type of expansion bolt characterized by a specially designed head. This head is designed to provide a larger contact area, resulting in improved force distribution. This can help to reduce the load on the connected component and extend the service life of the connection. DIN 2510 Form K expansion bolts are often used in areas where high load-bearing capacity and durability are required. They are often used in the mechanical engineering, automotive and aerospace industries to securely connect components that have to withstand high loads. | |||||||||||
| Thread (d1) | M12 | M16 | M20 | M24 | M27 | M30 | M33 | M36 | M39 | M42 | M45 |
| d2 | 8,5 | 12 | 15 | 18 | 20,5 | 23 | 25,5 | 27,5 | 30,5 | 32,5 | 35,5 |
| d3 | 8 | 12 | 14 | 14 | 18 | 18 | 25 | 25 | 28 | 28 | 32 |
| b2 | 13 | 16 | 20 | 24 | 27 | 30 | 33 | 36 | 39 | 42 | 45 |
| z1 | 1,75 | 2 | 2,5 | 3 | 3 | 3,5 | 3,5 | 4 | 4 | 4,5 | 4,5 |
| z2 | 4 | 5 | 6 | 6 | 6 | 6 | 9 | 9 | 10 | 10 | 11 |
| SW | 7 | 10 | 11 | 11 | 13 | 13 | 22 | 22 | 24 | 24 | 27 |
| DIN 2510 Form KU identifies a specific type of expansion bolt that meets the requirements of the German Industrial Standard (DIN) 2510. When installing a form KU bolt, which is characterized by a short thread and a spacer pin, the stress concentration in the first load-bearing threads on the shank side is reduced by an "overlapping" nut thread. This special shape is used exclusively in combination with double-sided capsule nuts up to M56 DIN 2510. Expansion bolts according to DIN 2510 form KU are used in particular for pressure vessel flange connections. | |||||||||||
| Thread (d1) | M12 | M16 | M20 | M24 | M27 | M30 | M33 | M36 | M39 | M42 | M45 |
| d2 | 8,5 | 12 | 15 | 18 | 20,5 | 23 | 25,5 | 27,5 | 30,5 | 32,5 | 35,5 |
| d3 | 8 | 12 | 14 | 14 | 18 | 18 | 25 | 25 | 28 | 28 | 32 |
| d7 | 8 | 12 | 13 | 16 | 18 | 21 | 24 | 26 | 30 | 32 | 34 |
| b2 | 13 | 16 | 20 | 24 | 27 | 30 | 33 | 36 | 39 | 42 | 45 |
| z1 | 1,75 | 2 | 2,5 | 3 | 3 | 3,5 | 3,5 | 4 | 4 | 4,5 | 4,5 |
| z2 | 4 | 5 | 6 | 6 | 6 | 6 | 9 | 9 | 10 | 10 | 11 |
| z3 | 11 | 14 | 16 | 17 | 19 | 19 | 21 | 23 | 23 | 24 | 25 |
| SW | 7 | 10 | 11 | 11 | 13 | 13 | 22 | 22 | 24 | 24 | 27 |
| DIN 2510 Form ZU identifies a specific type of expansion bolt that meets the requirements of the German Industrial Standard (DIN) 2510. Expansion bolts according to DIN 2510 Form ZU are used for pressure vessel flange connections. Similar to the KU form, this standard also defines the requirements for the design, materials and testing of these connections. The "ZU" form refers to a specific type of connection used in specific applications. | |||||||||||
| Thread (d1) | M12 | M16 | M20 | M24 | M27 | M30 | M33 | M36 | M39 | M42 | M45 |
| d2 | 8,5 | 12 | 15 | 18 | 20,5 | 23 | 25,5 | 27,5 | 30,5 | 32,5 | 35,5 |
| d3 | 8 | 12 | 14 | 14 | 18 | 18 | 25 | 25 | 28 | 28 | 32 |
| d7 | 8 | 12 | 13 | 16 | 18 | 21 | 24 | 26 | 30 | 32 | 34 |
| b3 | 27 | 31 | 36 | 42 | 47 | 50 | 53 | 57 | 60 | 64 | 66 |
| z1 | 1,75 | 2 | 2,5 | 3 | 3 | 3,5 | 3,5 | 4 | 4 | 4,5 | 4,5 |
| z4 | 7 | 8 | 9 | 8 | 10 | 12 | 14 | 14 | 14 | 15 | 15 |
| SW | 7 | 10 | 11 | 11 | 13 | 13 | 22 | 22 | 24 | 24 | 27 |
Installation and application instructions for expansion bolts
When using expansion bolts, the following points must be observed:
- Calculate the installation torque precisely – if necessary, with preload force measurement.
- Lubricate sliding surfaces to minimize friction.
- Take thermal expansion into account, especially in the event of temperature changes.
- Check for reuse – replacement is necessary if the yield strength is exceeded.
A brief summary of expansion bolts
Expansion bolts in accordance with DIN 2510 offer a reliable solution for highly stressed bolted connections. Their targeted elasticity protects against loss of preload and increases the service life of the connection – especially under dynamic or thermal loads.
Your individual expansion bolt offer - free of charge and without obligation!
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How to reach us
Monday – Thursday: 7:30 a.m. – 12 p.m & 1 p.m. – 4:45 p.m.*
Friday: 7:30 a.m. - 12 p.m. & 12 p.m.- 2:30 p.m.*
*except on public holidays in Germany
Our customer service team is there for you personally – friendly, competent, and always ready to listen.
Get in touch – we look forward to hearing from you!
Expansion bolts from Güldner - Highest quality for your application
Our screws and fasteners meet the highest requirements - precisely manufactured, tested and documented.
QualityWhat sets us apart
- Production according to DIN, ISO and customer-specific standards
- Documented quality assurance with test protocols
- Materials with certified origin
- Dimensional accuracy and strength tested
Certifications & Standards
- ISO 9001: Quality management
- Material testing according to EN & ASTM
- Traceability through batch numbers
Individual testing requirements? We are happy to adapt our test procedures to your specifications - just get in touch!
Your individual expansion bolt offer - free of charge and without obligation!
Do you have questions about our products or would you like to place an order directly?
How to reach us
Monday – Thursday: 7:30 a.m. – 12 p.m & 1 p.m. – 4:45 p.m.*
Friday: 7:30 a.m. - 12 p.m. & 12 p.m.- 2:30 p.m.*
*except on public holidays in Germany
Our customer service team is there for you personally – friendly, competent, and always ready to listen.
Get in touch – we look forward to hearing from you!
Expansion bolts from Güldner - Highest quality for your application
Our screws and fasteners meet the highest requirements - precisely manufactured, tested and documented.
QualityWhat sets us apart
- Production according to DIN, ISO and customer-specific standards
- Documented quality assurance with test protocols
- Materials with certified origin
- Dimensional accuracy and strength tested
Certifications & Standards
- ISO 9001: Quality management
- Material testing according to EN & ASTM
- Traceability through batch numbers
Individual testing requirements? We are happy to adapt our test procedures to your specifications - just get in touch!
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