High-quality expansion screws and expansion bolts according to DIN 2510

Expansion bolts and expansion studs (also known as screw connections with expansion shank according to e.g. DIN 2510) are unique fastening elements that have a unique property: They can expand under load. This property makes them an ideal solution for precise and secure connections in the industry. They are particularly suitable for constructions that are subject to changing operating forces and temperatures and where the durability of the screw connection needs to be ensured. The favorable behavior of expansion bolt connections is based on their elasticity, in particular the fact that they exhibit a greater elastic change in length with the same preload than so-called rigid bolt connections.

This behavior of expansion bolts leads to a number of advantages:

• Expansion bolts have a high long-term durability, as the additional loads on the bolts due to changing operating forces, thermal expansion and bending moments are reduced.

• The drop in preload, which contributes significantly to the loosening of the screw connections - during operation by creeping of the material, settling phenomena in the force-transmitting surfaces of the connection and the clamped parts, as well as by bending of the threads - is lower.

• Under certain conditions, the amount of preload applied can be easily measured via the change in length of the screw.

The following aspects must be taken into account when designing expansion bolts and expansion studs:

• The minimum length of the expansion shank should be at least twice, ideally four of the thread diameter to ensure sufficient elasticity.

• The ratio of thread core diameter to expansion shank diameter should be around 1.1 in order to optimize the load-bearing capacity and elasticity of the screw.

• The transition angle between the expansion shank and the thread should be kept relatively small. This leads to a favorable flow of force and better load distribution in the screwed thread.