this shows how to calculate length of stud bolt used in flanges & other purpose
https://www.superiorwasher.com/washers/8826/Copper-Washers.html
Here’s a clip that describes a useful hardware material in various applications including heating, plumbing and electronics. This material — copper washers, are the perfect choice for plumbing fixtures as the ductile and malleable material provides a bearing surface deformation that minimizes damage on the surface. Plumbing fixtures and household hardware assemblies require versatility and durability and this particular type of washer provides high-corrosion resistance.
You will find that washers made from copper material are a lot softer than other materials including brass, steel or bronze. As such copper washers allow even distribution of a fastener’s load reducing surface deformation that could be caused when fasteners are tightened. Learn more about this special type of washer with this video.