Brazing is a skill that approaches art. Do it right and it’s a thing of beauty. Do it wrong and you’re reaching for a can of spray paint to hide blobby abominations.
- To create smooth and strong joints, start with clean metal. Grind, sand or buff away all rust or paint until there’s bare metal an inch or more on each side of the prospective joint. If brazing new unpainted metal, clean with acetone or paint thinner to remove oily residue.
- Adjust the oxy/acetylene regulator for brazing. The optimum ratio of acetylene to oxygen is 1:1. Start with 5 lb. per square inch (psi) of oxygen to 5 psi of acetylene. Avoid acetylene pressures above 12 psi. Acetylene can self-ignite and explode above 15 psi.
- Select a brazing tip appropriate to the thickness of metal. The old farmer’s tradition of having one brazing tip for all repairs and adjusting the amount of heat by holding the tip nearer or farther from the work surface, nearly guarantees problems (see table below).
- Use tinted goggles. They will protect your eyes from spattering metal and allow you to comfortably see the color and condition of the metal as it’s heated.
- Always use flux. Flux cleans the base metal and protects the liquified brass of the brazing rod from reacting with atmospheric gases and contaminating or weakening the finished weld. Dipping uncoated brazing rods in powdered
- flux works well.
- Heat both sides of the joint to a dull red. Then touch the tip of the fluxed brazing rod to that red metal. The heat of the metal should melt the rod (not the flame). Weave the flame from the brazing tip slightly; the molten brass will move toward the hotter metal. Overheating the metal beyond bright red, to orange or yellow-hot, can boil the melted brass, blow holes in the metal and degrade the final weld.
Whenever possible, before brazing, find and use scrap metal of the same thickness and metallurgy to fine-tune oxy/acetylene settings and tip size. Attention to detail, practice and patience are the keys to brazed welds that look like artwork. FJ
