An old-school method that still gets the job done. Oxy-fuel cutting is a traditional yet highly reliable method of metal cutting. By combining oxygen with a fuel gas, it allows you to cut various types of metals with ease. In this process, the intense heat of the flame raises the metal to its ignition point, and a jet of pure oxygen oxidizes and separates the material. Thanks to its simple equipment, low operating cost, and ability to cut through thick metal sections, this technique is still widely used in heavy industries such as construction, shipbuilding, and industrial maintenance. In this article, we’ll take a closer look at what oxy-acetylene cutting is, how it works, its key advantages and limitations, and when it’s the most practical choice.
Oxy-fuel cutting — often known in the past as flame cutting — is one of the oldest and most proven metal cutting methods in the world. In this traditional process, metalworkers use a flame produced by mixing a fuel gas with oxygen. The most common fuel gas is acetylene, which is why the process is often referred to as oxy-acetylene cutting.
You might think the metal melts away under the intense heat, but that’s not quite how it works. It’s actually the jet of pure oxygen that performs the cut. The flame’s job is only to preheat the metal to its ignition temperature — roughly between 870°C and 930°C (1600°F–1700°F) for steel — at which point oxygen reacts rapidly with the hot metal, forming iron oxide. The molten oxide is then blown out of the cut by the oxygen stream, leaving behind a clean kerf. Unlike modern cutting methods such as metal laser cutting, oxy-feul cutting relies on a flame to preheat the metal before oxidation, giving it a unique simplicity and versatility.
This process works best for carbon steels and low-alloy steels, where the oxides have lower melting points than the metal itself, making them easy to remove. However, it’s not suitable for stainless steel, aluminum, or copper, since their oxides have much higher melting points and do not react effectively with oxygen.
At first glance, oxy-fuel cutting might look simple — just a flame and some gas — but behind it lies a precise chemical and thermal process. The operation takes place in five key stages. Let’s break down how it actually works:
Before anything else, the metal surface must be clean — free from rust, paint, or oil — since impurities prevent even heat distribution. The cutting torch is then adjusted for the correct fuel-to-oxygen ratio. If the mix isn’t right, the flame will either produce soot or fail to generate enough heat.
Once properly adjusted, the flame heats the steel surface to its ignition temperature (around 870–930°C / 1600–1700°F). At this point, the metal isn’t melted yet — it’s just hot enough to react with the pure oxygen that follows.
When the metal reaches the right temperature, a jet of high-pressure oxygen is released through the torch. This oxygen reacts rapidly with the heated steel, forming molten iron oxide. The molten material — known as slag — is blown away by the oxygen stream, creating the initial hole and starting point for the cut.
This reaction is sometimes referred to as a form of “rapid, controlled rusting” because it’s essentially accelerated oxidation.
Once the initial pierce is made, the torch moves steadily along the cutting line. Both the preheat flame and the oxygen jet remain active — the flame keeps the front edge at ignition temperature, while the oxygen continues to oxidize and blow away molten material.
Key factors like oxygen pressure, flame adjustment, and torch travel speed directly affect cut quality. If the movement is too fast, the cut will be incomplete; if too slow, the edges may overheat or deform.
In oxy-fuel cutting, the process relies on combining a fuel gas—such as acetylene, propane, methane, or propylene—with pure oxygen.
The flame produced by this mixture generates extremely high temperatures, heating the metal to the point where it reacts with oxygen and burns away (oxidizes), creating a clean cutting path.
But here’s the key: the type of fuel gas you choose directly affects the cut quality, speed, cost, and safety of the process. Each gas behaves differently—some produce a hotter flame, others offer better stability or lower operating costs. Let’s take a closer look at the most common ones
Acetylene produces the hottest flame among all fuel gases, reaching about 3,200°C (5,800°F) when combined with oxygen. It quickly heats the metal to ignition temperature, making it ideal for precise, fast cuts. However, acetylene is highly unstable and explosive, especially under high pressure, so it requires special storage and handling. It’s most commonly used in workshops, maintenance jobs, and cutting medium to thick steel sections.
Propane burns cooler than acetylene (around 2,800°C / 5,000°F) but has a broader heat zone, which makes it useful for larger and field-based cutting tasks.
It’s safer and more affordable, making it a popular choice for outdoor or heavy-duty industrial work. However, since its heat is less concentrated, propane cuts are slightly slower compared to acetylene.
With a flame temperature of roughly 2,700°C (4,900°F), methane burns cooler but offers excellent stability and wide availability. It’s cost-effective for large-scale or long-term operations, particularly where natural gas is already in use. This gas is typically used for thin steels and light-duty applications, rather than heavy industrial cutting.
Propylene and MAPP gas are blends of hydrocarbons that combine the safety of propane with temperatures close to acetylene.
They tolerate high pressures and are commonly used in automated or mechanized cutting systems.
You’ll often find them in heavy manufacturing, structural fabrication, and pipeline construction, where consistent, long cuts are needed
In oxy-fuel cutting, the final cut quality doesn’t depend only on the operator’s skill or the choice of fuel gas — a huge part of the outcome comes down to how well the equipment performs and how precisely it’s calibrated.
Here are the key components required for a safe and efficient oxy-acetylene cutting setup:
Two separate cylinders are used — one for oxygen (with over 99% purity) and one for the fuel gas (such as acetylene, propane, or methane).
Both must be stored under the correct pressure and handled carefully to prevent leaks or accidents.
Regulators are metal devices with adjustment knobs that reduce the high cylinder pressure to a safe working level.
For example, while oxygen cylinders may contain pressures up to 200 bar, only 2–5 bar is typically needed for cutting.
From the regulators, the gases travel through color-coded hoses — red for the fuel gas and blue (or green) for oxygen. These hoses must be rated for high pressure and heat to ensure safety and performance.
If you’re setting up or maintaining your cutting system, make sure your welding and cutting power supplies are properly regulated and inspected, as they play a crucial role in maintaining consistent flame control and overall safety.
The torch mixes the oxygen and fuel gas to create the cutting flame.
It’s designed with separate valves for adjusting the flow of each gas, allowing the operator to fine-tune the flame for the desired cut quality.
The nozzle or tip determines how the flame is shaped and how the oxygen jet is delivered.
Selecting the correct tip size depends on the metal thickness, type of fuel gas, and cutting conditions.
A properly chosen and maintained nozzle ensures a cleaner, smoother cut and helps reduce gas waste.
After understanding the gases and equipment, it’s important to look at the strengths and limitations of this traditional cutting method. Despite its age, oxy-acetylene cutting is still widely used in many industries due to its unique advantages. However, like any technique, it has certain limitations that should be considered before choosing it.
Among the various metal cutting methods, oxy-acetylene cutting remains a versatile and widely used technique. Its portability, simplicity, and ability to handle thick metals make it ideal for a range of industrial and educational settings. Here are some of the main applications
Used for cutting I-beams, thick steel plates, and large structural components, especially in workshops that build metal frameworks for buildings and bridges.
Since it doesn’t require electricity, it’s ideal for on-site work in mines, refineries, or industrial plants, where damaged components need to be cut or removed.
In offshore projects or pipeline construction, where metals are thick and environmental conditions are harsh, oxy-acetylene cutting is often the preferred solution.
Being one of the most fundamental metal cutting methods, it is commonly taught as the first cutting skill for apprentices and students in technical workshops.
Like any industrial process, oxy-acetylene cutting has a set of important guidelines that, if followed, improve both the quality of the cut and overall safety. To achieve clean, fast, and hassle-free cuts, consider these simple but crucial tips: