As mentioned previously, sometimes you may struggle with stems that break above the surface of the rivet head. Do not punch these back into the rivet. After the tank cures we carefully and “surgically “ buff the stem down with a sanding drum on a dremel type tool ,or use a fine sanding disc on a 90° air grinder. Just buff down the proud stem, not the entire surrounding area. Go slow as to not overheat the rivet area while grinding. Many times you will think you have a proud stem , but it is in fact simply a small aluminum cone that has extruded up the stem and into the rivet gun nose piece. These will typically look terrible while installing rivets, but many time be “knocked “off while wiping the excess sealant off the skins.
