Brazing is a technique that allows you to join and bond two pieces of metal permanently, using a torch and some form of filler metal. While brazing typically uses specialized brazing wire to bond the metals, you can substitute copper wire for brazing wire.
Clean the metals you plan to braze. Remove all oxidation with sandpaper. Remove all grease with acetone. Remove all dirt and grime with soap and water. Rinse with water to remove the residue from the acetone, sanding or soap, and then dry the metals.
Arrange the metals you plan to braze on a fire-safe work surface. Secure the metals with binding wire, a clamp or another tool if gravity will not hold the materials together.
Heat the metals until they are cherry red.
Paint the metals with flux at the seam, if they still show some signs of oxidation. You can skip this step, and braze without using flux, if there is no oxidation.
Place the copper wire on the seam once the metals are cherry red. Continue heating until the copper wire flows and joins the metals together. Allow to cool.
Always take fire safety precautions when using a torch.
Protect your eyes with goggles when brazing.
Work in a well-ventilated space when brazing.