Which types of bolts are not allowed to be reused?

A325 and A490 bolts are not allowed to be reused primarily because they are high-strength structural bolts that are subject to strict strength and performance requirements. When these bolts are installed, they are tightened to a specific tension, which ensures the structural integrity of the connection they are part of. Reusing them can compromise the bolt's ability to maintain the necessary clamping force, which can lead to connection failure under load.

The materials used in A325 and A490 bolts are also treated in specific ways to ensure their strength, and once these bolts are subjected to the installation process, they can undergo changes in their microstructure or surface condition that might affect their performance. As a result, it is recommended to use new bolts in critical applications to maintain compliance with the applicable design and safety standards.

In contrast, other types of bolts, such as A307 and A563, may have different reuse guidelines based on their material properties and intended applications. Galvanized bolts may also have specific considerations, but they can be reused if they remain in good condition and meet necessary performance criteria. Thus, A325 and A490 bolts are singled out for not being reusable to ensure the safety and reliability of structural connections.