Mending metal is a difficult job and requires a more permanent bond than glues or screws can provide. Instead, the task calls for a method called brazing -- joining metals with heat. Brazing uses lower temperatures than welding but higher temperatures than soldering, and it creates a stronger bond than soldering. Materials:
Metal to be brazed
Wire brush, grinder or abrasive paper
Clamps
Welding torch with mixture of MAPP gas and oxygen
Brazing rod
Flux
Flux filler rod
Safety goggles
Gloves
- Clean the joints of the metal with a wire brush, grinder or abrasive paper (figure A). A dirty surface cannot be properly brazed.
- Clamp the pieces to be joined together. For the strongest bond, make the gap in the seam as small as possible. (The pieces will be too hot to touch once they're heated, so do not try to adjust them.)
- Put on gloves and goggles before turning on the torch. Adjust the torch so that it emits only a small flame (figure B).
- Hold the torch about 1" away from the metal joint to heat it (figure C).
- After a few seconds of heating the joint, use a flux rod to sprinkle flux over the joint (figure D). The flux will remove the oxides on the metal.
- Remove the flux rod and continue heating the joint, moving the torch in a circular or zigzag motion. When the metal reaches the proper temperature, the flame will glow a dull red color.
- Touch the flux rod to the joint again, and direct the flame ahead of the melting rod tip.
- Continue heating the joint evenly and depositing flux until the two pieces mold together.
- After the metal cools, chip off the excess hardened flux.
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