Solid materials by friction welding. This method means that aluminium and Copper join through the heat, which develops when aluminium rotates against copper under pressure. This is a superior method to give a complete connection SMI’s Bi-metallic Connectors are made from aluminium purity equal to or greater than 99.5 %. The barrel is friction welded to the pin thus achieving the best possible transition between the copper pin and aluminium barrel. Barrels are capped and filled with grease so as to avoid oxidisation of the aluminium.