Gas Welding 101


I make things.

I've been gas welding cafe racer parts for a few years now, and although I use tig mostly, gas welding is a great way to get started in metal fabrication. In fact, if I weren't making parts for a living, I'd probably go with gas because its more portable than a tig, and the basic setup is thousands of dollars less. You will need better ventilation in your shop though, as gas welding puts out a lot of fumes and flux isn't good for your lungs, where a clean tig weld doesn't put out fumes at all unless you accidentally dip the tungsten.

Gas welding requires a cleaner metal edge than tig, tig will work fine with a fresh cut as long as there's no grease on it, but gas welding really requires a bright shiny edge. I like to use a deburring tool to cut a chamfer on the edge of each piece I'm joining, this gives better weld penetration and also ensures a clean weld area.

Use some clamps to line up the edges for tacking, usually I'll clamp one edge to start a tack, then tack down the weld line without clamps, as I can easily hold the parts in place once one end is tacked together.

I'm using a #1 welding tip for this job on 14ga 3003 aluminum. Since almost all my parts are the same alloy and thickness, I don't need a lot of different equipment. Common aluminum welding/brazing flux works great, just mix it with water until it's dissolved, I use about a teaspoon per ounce of water. One of the tough parts about gas welding is getting the flame the right heat and the right mixture. On a #1 tip, I like to have roughly a 10" flame, it's a good balance of enough heat to get the weld going and not enough to burn through too quickly. The mixture is determined by looking at the cone, or the bright blue flame coming right out of the torch, there are really two sections of the cone, the main cone and a tail, the tail is longer than the main cone and as you increase the O2, it will get shorter. For a good neutral flame (what you want for gas welding) the tail shouldn't extend out beyond the main cone, so increase the O2 just until the tail meets the main cone, don't go further or you'll have an oxidizing flame.

Flux is best applied to a hot edge, so it doesn't run away from the weld area. I give the weld edge a few passes with the torch and then brush the flux on, it should be hot enough that the water boils off immediately and leaves the white residue of the flux on the edge. Once the edge is coated, the parts are ready to weld.

For filler, I'm using .062 1100 tig rod, some people really like to use .030 welding wire, but I find this really too thin for my tastes, it's not stiff enough and tends to melt before hitting the weld puddle. The filler rod also needs to be fluxed for a good weld, so what I do is just set the torch on the bench facing up, and hold the flux brush to one side, then run the rod across the flame so the brush rubs against it after it's heated by the torch, any way you figure out how to coat the rod works just as well though.

Tacking is pretty easy, just apply the flame to the edges of the metal parts and once a shiny melt area starts to form, dab quickly with the filler, remove the flame and you're good. Welding is done pretty much the same as tig, keep the torch about 15 degrees off vertical and apply filler to the leading edge of the weld puddle. Starting the weld is the same as tacking, hold the torch so the main cone is about 1/8" off the surface, a weld puddle should form quickly, as it does, dab the filler rod into the front edge of the puddle (hold the filler about 15 degrees off HORIZONTAL, this keeps it from melting before hitting the weld puddle). Back the torch tip off the work about 1/4" and advance down the weld just a bit. Move the torch tip back to 1/8" off the metal and repeat. This is the basic technique, the rest is just fine tuning, you'll notice that the weld starts to get hotter the longer you're welding a part, so generally the torch tip is moved a bit further back as you go. This also happens as you get closer to an edge, most of the time, I don't approach an edge from the inside, but will stop about 1/2" short and weld the edge from the outside in.

Once the weld is done, a quick cleaning with a stainless brush takes the flux off, and the weld is ready for planishing, usually with a gas weld, the metal is soft enough that it can be hammered back into profile with the part, so no grinding is necessary or all that recommended. If the weld still hangs above the profile after planishing, filing the excess is okay.
Very cool man!
I knew I had a reason that i needed an oxy acetylene torch setup.
Posting for future referance.

(That is my classic response so I can find cool shit by searching that exact term later "spell check" be damned ;) )
I found an old torch at a yard sale for a Buck should I try and Use this or should I get a new outfit?
Top Bottom