What does compressed air and propane cut when used in a cutting torch? Why would you choose to use this combination of oxygen and gas to begin with? The oxygen referred to here is pure and used from a tank. Compressed air, on the other hand, is not "clean" or pure air or oxygen. It typically has impurities in it that make it a little less desirable for use in cutting certain metals. In order to use your compressed air and propane cutting torch in the most desirable manner, you need to know what you will be cutting. Pure air mixed with propane is generally hotter and more efficient than compressed air.
How It Works
Cutting torches, for cutting metal, are used to heat metal to high temperatures and then focus the air on the metal. The air combines with the metal at this high temperature and flows away from the cut as it's being made. The heat created does not melt but instead brings the temperature of the metal to the point of ignition. The most important aspect of the cutting is the flow rate of the air. If the flow rate is slow the cut will be ragged. If the flow rate is too fast, thereby providing too much air, the torch makes a wide cut that is concave. Cuts can be made beginning at an outward point along the edge of a piece of metal but they can also be made from the middle of a piece as well. Cutting from the middle is called piercing.
Using Cutting Torches
Safety is always the first place to begin when working with air and propane torches. Proper goggles and work clothes like thermal gloves and work boots are important. Remember, you are working with high levels of heat and very hot metal. Hot metal will flow out of the cut from the back so providing room on the backside of the piece for its exit is important. Heating the metal with the flame to a bright red is the first step. Providing the right flow of oxygen to this heated area is what begins the cutting process. The propane gas will require an injector torch because it is a heavier gas and needs a low pressure type of torch to run through the torch easily.