A 10mm double cap rivet, typically used in leather crafting and textile projects, can fasten materials with a combined thickness ranging generally from 5mm to 7mm.
Important Considerations for 10mm Double Cap Rivet Usage:

• Material Thickness: The rivet post needs to be slightly longer than the material thickness to allow for the cap to be properly set and secured. Some resources suggest adding ⅛ inch (3mm) to the material thickness when selecting the rivet length.
• Intended Use: Double cap rivets are primarily for securing and decorating purposes, not for heavy-duty load-bearing applications.
• Quality of Rivets: The strength of the join also depends on the quality of the rivets themselves.
• Installation: Proper installation is crucial for achieving a secure and durable hold. You'll need appropriate setting tools or a hand press to install them.
• Alternative Rivets for Thick Materials: If you're working with exceptionally thick materials, you might consider other types of rivets like tubular or solid copper/brass rivets, which are generally stronger.

In essence,a 10mm double cap rivet is suitable for materials with a thickness between 5mm and 7mm, allowing for a 3mm (⅛ inch) allowance for post setting. Remember to choose high-quality rivets and utilize the correct installation techniques for optimal results.