Brazing

Brazing is the act of joining two pieces of metal using a third metal as a glue of sorts. Where Welding melts the two pieces to become one, brazing does not. Brazing uses a filler rod often made of Brass because it melts at a much lower temperature than the pieces to be brazed together. It is very much like a much hotter version of soldering.

To braze you heat the two pieces up hot enough to melt the filler rod. If the rod alone is just headed up and applied to the pieces to be bonded, it will be a very week joint.

Cleaning
The pieces to be brazed together need to be very clean in order to create a strong joint. Metals are machined with oil as a lubricant, so all of this needs to be cleaned off, as well as any rust, oxidation or coating the metal may have. Sanding or filing the pieces before brazing is often required. If you are using tubes, you need to clean the inside of the tube a few inches as well.

During the brazing process a cleaning solution called flux can be used to "wet" surface so the brazing rod can flow into cracks and tight areas easier.