Versatile Mig Welding - Weld With Gas

Start at an end of the piece to be cut and heat until it is cherry red. Once it starts to liquefy, press the burst valve lever and make your cut. Move as fast as the torch will allow a clean cut to keep the heat of the flame confined to a small area. If you move too slowly, you could heat the area around the cut so much that it will also liquefy. When this happens, it can become elastic enough that the metal will close back up behind the torch.

Now slowly open the secondary oxygen valve and adjust until you get a neutral flame. You will recognize it by its characteristic blue tint and bright inner flame cone.

An alternative to oxyacetylene cutting is to use a plasma cutter like our Miller Spectrum 375, which can run on 110- or 220-volt current. It makes extremely neat cuts with a smaller kerf, or cutting width. Even though prices on plasma cutters are coming down, they are still expensive, and you need an air compressor to use them. Plasma cutters use a high-amperage arc to make the cut but need to be connected to compressed air, which blows the slag away.

Here is a comparison of a plasma cut (left) versus an oxyacetylene cut. Notice how the plasma cut leaves distinct edges or ridges in the cut, while the flame cut has a softer appearance. The plasma cutter also leaves a small ridge of slag below the cut area that needs to be ground away.

Gas welding is the oldest welding process. It could also be considered a dying art. It is definitely a skill that has fallen out of fashion as the prices of MIG welders have dropped. It is a good skill to learn, and the technique is similar to TIG welding, so it's good practice for a guy who plans to one day buy a TIG welder. For this demo, we used a No. 0 welding tip, the smallest in our kit, and some ER70-S6 welding rod, the same as we use for TIG welding. We set the regulators to about a 3- to 5-psi flow rate for both oxygen and acetylene and adjust to a neutral flame. Ideally, the flame will be just hot enough to liquefy the metal. Not enough heat makes for wide, sloppy, and uneven welds, while too much heat will obviously burn holes through your work. You'll need to experiment a lot to get your flame dialed in. Like TIG welding, oxyacetylene welding is done right to left. To avoid burning through, begin just inside the edge of your joint. As it liquefies, you can back the torch up to the edge and add the filler rod. Once under way, you need to move pretty quickly with a smooth rhythm of dipping the filler rod and moving the torch to the left. If your travel is too slow, your chances of burn-through increase exponentially. By the time you reach the left edge of your joint, the work could have so much heat in it that a giant hole could seemingly appear out of nowhere. Remember, as you're traveling along the joint, you're pushing heat toward the edge of the piece, and it can only absorb so much heat before it melts. You can control this by using a hot, narrowly focused flame and welding quickly, or you can modulate the temperature by doing a section at a time, pausing to allow the work to cool for several seconds. This is a technique similar to stitch-welding with a MIG machine.