I am building a boiler similar to the PM Research vertical boiler. I am using 3inch od copper pipe with about 1/8 wall. I am also using ends made of a similar material. What size rivets should I use to join the ends to the boiler? I was wondering what size would be good and a good source? In the US it seems our choices are limited in model engineering suppliers, and sort of at their mercy for product. Is there an industrial supplier that sells the type of appropriate rivets? Does anyone fashion their own from copper wire?