Aluminum Welding Part 3
Oxy Acetylene Welding Rules

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WELDING RULES

Note: The following procedure is for oxy acetylene, because of the more technical nature and varied availability of hydrogen.

The rules are simple. Follow them or fail!

Open the oxygen bottle fully to seat the upper packing, then just crack the acetylene. Set regulators to equal pressures, from 2 to 5 pounds each, with smaller tips needing lower pressures.
Choose a torch tip one size larger than would be used on steel, i.e. If choosing a 00 (double ought) tip for .040 steel sheet, then move up to an 0 tip for .040 aluminum sheet.
If oily, clean the material with solvent, lacquer thinner. or alcohol. Scrub with stainless brush on both sides just prior to welding.
Flux either the rod (or wire), or the part -- or, in extreme cases, both. The flux will be a white powder which will be mixed 1/3 with either 2/3 water or alcohol.
Safety precautions such as eye protection, adequate ventilation, and keeping one's head out of the fumes, are recommended.
Choose the proper filler metal for the alloy to be welded. Common weldable aircraft alloy sheetmetals are shown in Figure 2.

Hollow, flux filled rod, was made available years ago, but aside from the questionable alloy, it had the persistent bad habit of neatly dividing itself, building up the edges of the joint without joining them together.

See The TM Meco Torch and other welding supplies

Oxy-acetylene- top view.

Oxy-acetylene weld, back (or root) side. Perfect penetration like this is standard with the torch. TIG/GTAW can do it, but needs a steady back-purge of argon to accomplish this. Not cheap!