An oxyacetylene cutting torch is a dangerous tool, but with the right precautions and a little practice you can use it to cut steel to size and into different shapes. To learn how to do this, read on.
Steps
Method 1 of 3: Preparation
Step 1. Understand the basics of the cutting process
The initial heat produced by the combustion of acetylene is capable of melting steel. By adding a stream of pressurized oxygen, the flame cuts the metal along a precise line. Steel and carbon steel are the only materials that can be cut. Aluminum, stainless steel and other materials and alloys cannot be cut with an oxyacetylene torch.
Step 2. Get the right tools
Before assembling everything (procedure that will be described later) you must have:
- Fire extinguisher. For most cases a compressed air and water fire extinguisher is fine, but on oil, plastic and combustible materials an "ABC" class is required.
- Tools for measuring and drawing cutting lines. This way you can be sure that you are doing the job correctly. You will need a ruler, square and a soapstone "chalk".
- Safety equipment which includes welder's goggles and heavy leather gloves.
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Suitable clothing, practically mandatory. Do not wear loose clothing made of flammable synthetic fabric or dresses with fringes and torn edges, as they can catch fire more easily than those that are well-hemmed and close to the body. This also means no partially ripped pockets or flapping shirt cuffs; flame retardant clothing would be appropriate, but if not available, wear something cotton and snug. Nylon and other synthetic fabrics widely used in clothing catch fire immediately!
- Sturdy boots with a leather sole: are highly recommended, because those with rubber soles, when they come into contact with incandescent slag, burn quickly. In addition, lace-up boots are preferred because the boots that simply slip on (such as the cowboy ones) are wide at the calf and the melting slag can fall inside.
- A flintlock to ignite the flame correctly. Using matches or lighters is very dangerous; a specific flintlock for oxyacetylene torches reduces the chances of injury.
Step 3. Set up your work in a safe area
It is recommended to use the torch on bare earth or on a concrete surface as sparks can fall several meters from the torch. Dry materials such as paper, sawdust, cardboard and dry leaves / grass should be moved at least 4-5m or more. It prevents the flame from coming into direct contact with the concrete, especially if it is fresh, as it could cause it to dilate and violently break with consequent flying splinters of concrete.
Step 4. Place the piece you need to cut on a stand and work surface at a comfortable height
A steel table is ideal because it allows you a stable support while you heat and burn the piece to be cut. Never use surfaces that are flammable or onto which flammable products have been spilled. Furthermore, check that the surface has no metal oxide coating, such as lead paint, chrome primers and zinc plating because they emit toxic fumes when inhaled.
Step 5. Draw the cutting lines with the soapstone, which allows you to make adjustments if some precision is required
If you don't have soapstone available, use a permanent marker, but remember that the mark tends to disappear as soon as it comes into contact with the flame. For high-precision cuts, you should use a special saw, which is not the subject of this article.
Method 2 of 3: Mount the Cutting Torch
Step 1. Attach the gauges to the right cylinders
Usually the tubes and the oxygen tank are green while the acetylene ones are red; they are coupled with the separate ends to be connected to the respective cylinders. The acetylene tube has an inverted weft with male-type fittings to avoid interchanging the tubes and gauges. The fittings are made of brass and can be easily damaged, tighten them with the right size wrench.
Step 2. Make sure the acetylene regulator is closed by turning the knob back a couple of turns, then turn the gas valve located above the bottle
Open it with just one turn of the wrist. This is done for safety reasons. Never allow the acetylene pressure to exceed 15 PSI since at high pressures the gas becomes unstable and can ignite or explode spontaneously. Here's how to adjust the acetylene to the right pressure:
- After opening the main cylinder valve, open the regulator by turning the knob clockwise. You have to do this very slowly while always keeping an eye on the pressure gauge. Open the regulator until the gauge indicates a pressure between 5 and 8 PSI.
- To bleed the pressure from the hose, open the valve on the torch until you hear the gas escaping, then check the pressure gauge to verify that the pressure remains constant during the flow, this way you can be sure that the regulator is set correctly.
- Close the acetylene valve on the torch.
Step 3. Close the oxygen regulator and adjust the pressure
Turn the regulator down and then up for a couple of turns. When you're done, proceed like this:
- Fully open the main valve on the oxygen cylinder. This is a dual outlet valve and if it is not fully opened, there is an oxygen leak around the stem and seal due to the high pressure (2200 PSI).
- Open the regulator slowly and check the pressure gauge as you do so, the pressure should remain in the range of 25 to 40 PSI.
- Open the oxygen valve on the torch to relieve the pressure inside the tube. Note that there are two oxygen valves. The one near the pipe fitting controls the flow of oxygen to the mixing chamber for combustion, for both the heating operation and the cutting jet. In this way there is no oxygen escaping from the tip of the torch until the trigger is squeezed or the valve closest to the torch is opened. To get started, open this first valve with several turns to make sure there is enough oxygen for both functions (heating and cutting). Then open the front valve slightly to drain the hose (3-5 seconds for a 7.5m hose).
- Close the front valve.
Method 3 of 3: Using the Torch
Step 1. Put on gloves and safety glasses before lighting the flame
Check the work area one more time to be sure there are no flammable materials. At this point, you are ready.
Step 2. Turn on the flame
Open the acetylene valve letting the oxygen escape from the mixing chamber for a few seconds. Then close the valve just enough to hear only a slight hiss of gas. Grab the steel and hold it in front of the tip of the torch, where the spark is generated. Squeeze the lock with your hand. A small yellow flame should light up at the tip of the torch when the spark ignites the acetylene.
Step 3. Adjust the acetylene valve until you get a yellow flame about 10 inches long
Make sure it comes out of the tip of the torch; if fed with excessive amounts of acetylene, the flame may jump or escape from another opening other than the tip.
Step 4. Slowly open the front oxygen valve
The flame turns blue because there is enough oxygen for the acetylene to burn completely. Increase the oxygen until the flame begins to shrink towards the tip.
Step 5. Open the oxygen valve further to increase the length of the internal flame, so that it is slightly greater than the thickness of the steel you need to cut. Well)
If you hear pops or the blue flame seems out of control and untidy, there is probably too much oxygen; reduce it until the flame becomes stable and the internal one takes on a precise cone shape.
Step 6. Bring the tip of the inner flame to the surface you want to cut
You have to heat the steel with this flame until a pool of molten metal forms and the section becomes incandescent. If you have a 6mm piece of steel at room temperature, it will take 45 seconds for it to transform into this state. However, more time is required for heavier or colder metals. Keep the tip of the flame steadily 9 mm from the metal and concentrate the heat in a single point.
Step 7. Squeeze the cutting “trigger” down to release the jet of oxygen, this will ignite the molten steel
If a violent reaction sets in, the steel has caught fire and you can gradually increase the pressure until the flame has cut through the entire thickness of the metal. If there is no reaction, the metal is not hot enough, so release the trigger and continue to heat the area.
Step 8. Begin moving the tip of the torch slowly along the cut line when the flame has passed the thickness of the steel
You should see that almost all the sparks and castings protrude from the top and bottom of the cut. If the flow of this glowing material slows down or backs up, reduce the cutting speed or stop to allow the metal to heat up a little more. It is better to cut too slowly than too fast.
Step 9. Continue until you have split the metal and finished the cut
Make sure there are no bits of molten metal and sparks under your feet; even the sturdiest soles of boots can burn if you step on a large piece of metal.
Step 10. Cool the metal with plenty of water
Alternatively, if you're not in a hurry, wait for it to come back to room temperature naturally. Remember that dipping a piece of hot steel into a bucket or stream of cold water will instantly generate a cloud of boiling steam.
This advice only applies to mild steel as water cooling can damage hardened steel.
Step 11. Remove the debris from the cut
You can sand the cut line if you want a precise finished job.
Advice
- Make sure all hose connections, control valves, gauges and other connections are tightly closed. Gas leaks could immediately cause a fire.
- Always carry gas cylinders upright.
- Keep children and animals away from areas where you work with the flame.
- Keep the tip of the torch clean at all times.
- It is better to install a backfire safety valve on both ends, it is much safer than having only one.
Warnings
- Use this tool only in well-ventilated areas and away from combustible materials.
- In some states, safety regulations require another person with a fire extinguisher to be present when working with open flames.
- Use a safety valve to prevent backfire.
