Oxyacetylene welding

When it comes to welding, Oxyacetylene welding is considered a good introduction to the practices. While it is not as sophisticated as the other processes (TIG, MIG, GMAW, FCAW, and on and on), it makes for a good starting point and has many applications.

Legal Disclaimer: By reading this, you agree that you are to be held responsible for your own actions and that I have in no way influenced your decisions and shall not be held repsonsible for your actions. Disclaimer: Expect to fail. Use common sense. Don't play with fire. Work with it.

Why Oxyacetylene Welding?

• Oxygen and acetylene combine into oxyacetylene to form the hottest burning and most widely available combination of gasses. MAPP gas burns at a paltry ~3000 degrees centigrade, while Oxyacetylene will manage 5500 degrees centigrade at stoichiometric ratios.
• It is comparatively cheap to start. A brand new great torch set will run you $300, add on a couple tanks and filler rod and you're ready to roll. Machines for MIG, TIG, wirefeed and what not start around $450 for a, "good enough," setup, while a great setup can run up to a grand. Add in a tank of gas for some processes and the consumables and you're in the hole a lot worse than if you'd stuck to oxyacetylene.
• Portability. Putting a set of cylinders in the bed of a pickup is considerably easier for a single person than putting a machine in there.
• Ease of learning: Assuming you set the right line pressures, choose the right tip for the job, set the flame up correctly and clean the piece, oxyacetylene welding becomes a breeze to learn.

Why Oxyacetylene Cutting?

Yet again, portability. Sure, you can pick up a plasma cutter and have smooth, cold cuts, but an Oxyacetylene setup is cheaper (in my experience), more reliable, and as versatile. You can set up a rail-guided cutting torch that will cut extremely precise lines. You can use a mechanized rolling torch, which will allow you to hand-cut things precisely. You can use electromagenetically guided jigsaw-like setups to cut out odd shapes. Oxyacetylene cutting is easy, simple, portable and cheap.

What you'll need

• A clean place with a heat-proof surface and plenty of room and ventilation. A good surface would be rough bricks similar to those used on the space shuttle but severely less expensive and more widely available. A smaller ratcheting holder that is elevated will make verts and horizontals possible, as well as making starting outside and inside corner welds easily startable.
• 1 cylinder of Acetylene
• 1 cylinder of Oxygen
• 2 regulators: 1 fuel and 1 oxygen
• 2 hoses: 1 oxygen and 1 fuel
• 1 torch barrel
• 16 gauge sheet steel, preferrably cut into 2"x4" pieces
A striker
• 1 10" Crescent Wrench, maybe even a 12"
• 1 large set of locking pliers
• A set of tip cleaners
• A wire brush
• double ot (00) and triple ot (000) welding tips (the triple ot is handy for heat control on verts)

I am going to cover 16 gauge (1/16") steel (silicon-covered) here on how to prep it, adrogynous welds, filler metal welds, and a bit of braze welding.

Safety

Yes, I made that title bigger than any other title in this node for a reason. Simply put, there are a lot of ways to endanger oneself while gas welding. So we need to prepare where you're going to work and what you're going to work on and the environment in general. The easiest way of putting it is to have all you equipment in good working order and don't weld in any place you wouldn't be able to breathe if it was filled with, say, argon.

Safety Equipment

1. Ventilation: Can't breathe? You die. Make sure you're doing this in a well-ventilated area. Put a fan near, making sure to blow the welding gasses away.
2. Eyes: I cannot say this enough, WEAR GOGGLES! Wear Industrial-strength goggles. You should be able to pick them up from an auto parts store. Whether or not they have a shield that you flip up or an integrated shield is up to you. But, wear them at all times when there is a flame or an arc around. If you do not, you are likely going to get arc flash at some point, which will cause damage to your eyes. And it keeps things out of your eyes.
3. Body: Wear TIG-design gloves. They're light, more flexible than heavy process gloves, will last for a long while. But more importantly, they keep your hands safe. Wear them constantly, unless you're sandblasting a piece. It makes handling metal safer intially (prevent cuts) and keeps your hands safe from burns (though they're not heat-proof; heat will soak through eventually). Speaking from experience, let me repeat: Wear them if there is metal near. I lost use of my left thumb and index fingertips for a week becuase I picked up a hot piece of filler rod, without realizing. If they make you feel safer, you can wear chaps and a coat, or pick up a good pair of Carhartt coveralls. Just be aware if you skip the coat or don't cover your arms, you'll look like you've freckled up when you're doing verts. I don't wear the coat that often, unless the position generates a lot of sparks. I also wear a pure cotton cap that covers my hair completely. Burning hair is not a good thing or smell.

Safety Procedures/Precautions

These are merely simple steps you should take to prevent harm to yourself.

1. I shouldn't really have to say this, but I will anyways: Never point the flame at a person. It is burning at a heat in excess of that a human can withstand. Absolutely positively never ever think of bringing the flame near anyone's skin.
2. NO GREASE OR OIL ANYWHERE! (Same goes for all flammable things, really.) This is absolutely essential. Do not use grease or oil anywhere near the piece, on the cylinders or within ten feet of the flame. It will cause an explosion. If you must lube something up, use soapy water.
3. Secure the cylinders. Yet another simple thing, just bolt a couple chains to something, place the cylinders behind them and make sure they're fairly stable and pointing straight up.

4. Do a leak check! Connect all the hoses, the torch barrel and tip. Make sure your cylinders are closed, very important. Also, make sure the regulator screw is backed out all the way. At this point, check your tip size on the chart that should've came with the setup or the poster in a shop, make sure it is the proper size tip for the thickness of the metal. If it isn't, find the correct size tip and replace the one on the barrel. Now, check the table for the fuel you're using, and find the fuel pressure and the oxygen pressure you will need. What you need varies upon tip size/metal thicknes. It is essential that you only hand-tighten the tip bolt, because there is an o-ring that you can damage if you tighten it too much. The barrel and gas lines can be secured with a wrench to ensure sealing. Secure the regulator on each cylinder cylinder; secure all the connections. Close the valves on the torch barrel. (Important note! Oxygen valves close righty-tighty; Fuel gasses close Lefty-tighty. This prevents connecting the oxygen and fuel gas in the wrong places.) Now, for the oxygen, back the regulator screw out all the way. This makes sure it won't fly out and ping you. Now, slowly open the cylinder all the way, until you cannot turn the knob any further. Turn it in reverse one turn. You do this because it is a back-seating valve, a safety feature. Now, slowly, very slowly, twist the regulator screw in, until you get some pressure in the line. For the acetylene cylinder, put it one and a half turns, as it is not a back-seating valve. Using the regulator screw, set the line pressues (according to the smaller pressure gauge on the regulators) that you will require for the tip size.

   Spray down every connection with soapy water. After filling each line, back the regulator screw out and watch for bubbles. If there are any bubbles whatsoever on the gas lines, try tightening them up and see if it solves the problem. If that doesn't, you need new hoses or take them to someone who can splice them back up to make them not leak. Watch the regulators, also, because they will indicate if there is a leak by showing the line pressure as decreasing or the cylinder pressure. If the cylinder pressure is decreasing, you need to make sure that the regulator is secured. If the regulator is secured and the cylinder pressure is still decreasing, you've got trouble and here is what to do: Close the cylinder valve (the one on top of the cylinder itself), twist the regulator screw to equalize the cylinder and line pressure and slowly open your valves on your torch without igniting the torch. Close the valves on the torch, back out the regulator screws, close the cylinders, and remove the regulators. Immediately call the supplier of your tanks and vacate the area. Assuming you have no problems, after a couple of minutes of holding their pressure, the lines and cylinders are ready to be used.

   It is important to do this often, though not more than once a day. Use the time to go get a cup of water. (Not coffee! Caffeinated blood makes for jittery welds.)

5. Do not let the gasses run freely without being ignited. Do not ever use the gasses to "clean" things. Oxygen lows the combustion point of things. IE: It may just turn your "dirty" pants into "explosive" pants. Bad things.

Preparation

The saying goes that an ounce of prevention is worth a pound of cure. In welding, prevention is great, but preparation is better. When you're working with coated metal, it is best to sandblast it clean if at all possible. Be sure to sandblast both sides of the metal, because though you won't be welding the backside, it will affect heat distribution and weld quality.

The sandblaster I used was a fairly simple setup and not difficult to work at all. You would unlock the door on the side, place the piece in the cage, and close and lock the door. Head back out to the front safety glass and put your hands in the gloves inside the booth. Pick up the gun and aim it at the pieces, step on a pedal and out comes the sand at high speed. If the pieces were silicon-coated (a dull gray before), they should be somewhat silvery. Manipulating the pieces was decidedly less fun, because the gloves are not dextrous. After that, it's a matter of unlocking the door and taking the pieces out.

Setting up

As put in the safety section, secure your cylinders, do a leak check, secure all lines and connections. Prep the metal. Get your goggles, put your gloves on and prep them metal. You'll start with a double-ot tip and do an adrogynous bead. Running a bead is the most difficult thing about this. Once you learn to run a bead, everything else is pie.

Make sure to check your pressures that you'll need again. When you bought the tip, there should've been a chart listing the pressures. Screw all the connections in. If a nut has a line running through the middle of it, it will be a lefty-tighty connection and for fuel gasses only. Secure the lines into the torch barrel using a wrench. Then, place the tip on the barrel, and tighten it with your hand, maybe one rotation with a wrench (any more and the o-ring is at risk of cracking). For a double-ot, it should be something like 5-15 PSI on both oxygen and acetylene, but look at the chart to be absolutely sure. Close the valves on the torch barrel. Now, make sure your regulator screw is backed all the way out, open the oxygen cylinder all the way and then out one turn, open the acetylene cylinder a turn and a half.

Push the regulator screw in until the line pressures are set according to the chart pressures for the tip. Lay the piece of steel (you will only need one clean piece for this) flat on the workbench. Prop your goggles up so you can put them on in a minute, ready your striker, wedge the barrel so that you only need one hand to open the fuel gas valve. Open the acetylene valve slightly, hit your striker in front of the tip and watch your hands. You should have a nice little flame. Continue opening the valve until your flame starts smoking. Then, turn it down until it just stops smoking. Now put your goggles on for the duration of the weld. Slowly open the oxygen valve. Opening it too quickly will result in the flame dying out, in which case you should turn off the acetylene quickly, as well as the oxygen. Your flame will turn blue, and you will soon notice a flame within the flame. Continue adding oxygen until the flame inside the flame (the primary flame) is about a half an inch long. It should be slightly fatter than a normal cone, more bulged, but not horribly moreso.

It is important that you now find a position in which your arm won't die while you lay the torch horizontal.

Place the tip so that the primary flame is on the steel. You will want to swing the flame left and right across the width of the steel, so that no one particular place gets too hot. Pick a side of the metal, lengthwise, where you wish to begin your bead. Now, dip the primary flame down towards the metal. In the place where you wish to begin, start swirling the tip around slightly, until a small puddle of molten metal forms. Begin to move the puddle by pushing it from its backside, zigzagging up and down, pushing it towards the opposite side of the metal. If you leave the flame in one place too long, it will glow cherry red, then begin to spark. Either get moving or watch a hole get cut through your workpiece. A really nasty hole. Expect this to happen multiple times before you can gauge how much time you will need to hold it one place or how fast you will need to go. Once you finish with that bit, take your torch away from the metal, turn off the barrel's valves and the flame should go out. It is now okay to take the darkening goggles off, but you should be wearing safety glasses or goggles.

Once you've been able to run a bead that is nice and clean, does not impart slag on the other side of the metal and the work side, you will be ready to move onto adrogynous corner welds.

You will want to have a brick or something non-flammable that you can move available for this bit. Also, you will need a piece of copper filler metal rod. Set up the cylinders, get the welding torch ready, and get two pieces of 2"x4" 16 gauge. Place one piece flat down, with the other perpindicular (the long sides touching) and make it stay with the brick. Fire up the torch and now you'll learn how to use the rod. Simply heat the edge up about a quarter inch in on either side (make sure both pieces are equally heated, glowing the same color), place the flame down in there, and dip the rod in and let it break a bit off. The puddle will form with the filler metal, and you simply want the pieces bonded together at a 90 degree angle. This is basically a stitch weld on 90. Once they are bonded on both ends, you're good to go. Set aside the rod and move along.

Use locking pliers to pick up the L-shaped piece of steel, place it so the corner is facing upward. The procedure here is essentially the same as running a bead, but it can be more frustrating because you now have two pieces to deal with. If the pieces aren't heated at the same rate, then you will probably get holes through the corner. You're aiming to make a 90 degree corner, except the weld will probably make it less pointed and more rounded.

Once you've managed to get adrogynous corners down, it's time for filler metal mania. You'll want copper filler metal rods, easily purchaseable at most welding shops and auto parts shops. Don't get much bigger than a 1/16" diameter.

Filler metal welding

Doing filler metal welding is similar to adrogynous, position-wise. It is easier in some aspects and more difficult in others. First off, the filler metal rod acts as a heatsink. As you dip it in the puddle, it the puddle will get smaller and cooler. This is essential, because it will prevent the puddle from burning through (although, if you just shove the rod in, it will go straight through and make the back look really ill). It will be harder in the sense that there is more metal there to manage.

This is also where we introduce positions. There are flat, horizontal and vertical positions, lap, corner and butt welds. Flat is simply laying the piece on the ground and running a bead. Horizontal is where the piece is perpindicular to the ground and you run a bead across the piece. Vertical has the piece in the same position as the Horizontal, except you will run a bead upwards, from the bottom. The welds can be done in any of those positions. Corner welds are like adrogynous corners, except you can use filler metal. Lap welds will have you placing one piece of metal on top of another offset, and running a bead down the edge of the top one. Then you flip it over and run it down the back side. Butt welding is when two pieces are places edge to edge and the edges are welded together.

Running a bead with the rod requires the same steps for setup, so don't worry there. Once you get it fired up, you will have to hold the torch with one hand and the rod in the other. Start a puddle, then dab the rod in, enough that it melts, but not enough to cool it off to where it is not glowing. Run the bead, trying to dab the metal in consistently, so that the bead is of equal width and height through the whole piece. If you need to restart, drag the flame back about 1/4" behind where you stopped. That's it. Run each weld type in each position.

Notes: I prefer to use a triple-ot on verts. The verts are especially difficult because they heat very quickly and are easy to burn through on, so the triple-ot's lower heat capacity is much nicer. Use a stitch welder, if you have access to one, on the pieces you're lap welding. It's very handy.

Braze welding

This just the next logical step in the chain. It is like filler metal welding, except cooler. You will need brass filler metal rods, along with braze powder. You'll want to do this in all the positions and kinds of welds as filler metal, trying to keep the height and width similar throughout the length of the bead.

Set up the torch and piece as normal and get the brass rod. Poke a hole large enough that you can put the rod through it in the top of the canister of braze powder. Fire up the torch, adjust the flame. Now, instead of starting a puddle on the metal, heat it up. Not too hot, not cherry red or nearly that hot. Just warm. Now, take your metal rod and heat the last few inches up just slightly, a couple of swooshes should do it with the torch. Quickly dip it into the braze canister through the hole you poked earlier. Pull it out and it should have white powder on the part you heated up. Now, place it right above where you want the bead. Heat it up with the torch and it should dribble down a bit. Then, after you start it, you can dip it into the braze puddle. Once you start getting lower on the white braze powder, you should heat the rod up some more and dip it back in the powder and start again from where you stopped.

The reason you use braze powder is to stabilize the puddle and coat the braze once it is cooled. You'll notice a chalky substance on the braze if you scratch at it after it has cooled significantly. This keeps it from rusting, I think, though I am not entirely sure.

Cleaning up

Once you're done welding on a piece, you can wait for it to cool off or pick it up with the locking pliers and run over it with the wire brush. Make sure your goggles are on, because the slag goes everywhere, including your eyes. After you're finished for a few hours or more, you should seal up all the valves and make sure no one approaches it with grease or oil. You can clean the pieces again in the sandblaster to see your primo job in all its glory.

If I have gotten anything wrong here, please /msg me right away if you don't mind. Big ups go to Chris Hobson, my welding instructor for being one of the nicest guys around. Edited: According to lj's notice, I forgot some of the improper oxyacetylene placements. Made the corrections, added a tiny bit and correctly spelled some words I'd misspelled. Edited again: The node has now been properly formatted in HTML (as opposed to tons of line breaks, bad lists and no paragraphs) and some spelling errors have been corrected. Some things were added, while others were rewrote for clarity. Please notify me of any changes that need to be made, as usual.