We’d like to share with you one of the technical questions that came to our blog! One of our readers needed to purchase a screw capable of withstanding 5 million cycles at 1 Hz under shear and tension. Let’s discover together the other requirements for screws subjected to shear and tension, along with the response from our technical expert Alessandro.
The technical question: all the specifications.
In addition to what was specified above, the screw also needed to have the following characteristics:
- Diameter: 6.3 mm
- Type of stainless steel: AISI 304/A2 or AISI 316/A4
- Minimum length: 50 mm.
Some considerations about strength.
Typically, standard screws in AISI 304/A2 and AISI 316/A4 quality are not designed to be subjected to shear, only tension. The maximum strength obtainable is class 100 (MPa or N/mm²). Therefore, if the screw is to be subjected to shear, it is necessary to use structural screws:
- EN 15048 (to indicate non-preloaded assemblies, generally used for shear joints)
- EN 14399 (to indicate preloaded assemblies, suitable for friction-based joints).
Screws subjected to shear and tension: which material to choose?
Furthermore, the indicated diameter (6.3 mm) suggests a self-tapping screw, which is not designed to work under tension. In this case, it is even more challenging to use the previously mentioned quality materials (AISI 304/A2 and AISI 316/A4). Screws of this type are designed to join two sheets of metal, and the values considered are:
- Core hardness
- Self-tapping capacity
- Torsion resistance.
Consequently, for the job indicated in the technical question, it is preferable to choose different materials. However, it is first necessary to understand the operating conditions and the corrosive agents involved.
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